BOOK XII.

Previously I have dealt with the methods of separating silver from copper. There now remains the portion which treats of solidified juices; and whereas they might be considered as alien to things metallic, nevertheless, the reasons why they should not be separated from it I have explained in the second book. Solidified juices are either prepared from waters in which nature or art has infused them, or they are produced from the liquid juices themselves, or from stony minerals. Sagacious people, at first observing the waters of some lakes to be naturally full of juices which thickened on being dried up by the heat of the sun and thus became solidified juices, drew such waters into other places, or diverted them into low-lying places adjoining hills, so that the heat of the sun should likewise cause them to condense. Subsequently, because they observed that in this wise the solidified juices could be made only in summer, and then not in all countries, but only in hot and temperate regions in which it seldom rains in summer, they boiled them in vessels over a fire until they began to thicken. In this manner, at all times of the year, in all regions, even the coldest, solidified juices could be obtained from solutions of such juices, whether made by nature or by art. Afterward, when they saw juices drip from some roasted stones, they cooked these in pots in order to obtain solidified juices in this wise also. It is worth the trouble to learn the proportions and the methods by which these are made. I will therefore begin with salt, which is made from water either salty by nature, or by the labour of man, or else from a solution of salt, or from lye, likewise salty. Water which is salty by nature, is condensed and converted into salt in salt-pits by the heat of the sun, or else by the heat of a fire in pans or pots or trenches. That which is made salty by art, is also condensed by fire and changed into salt. There should be as many salt-pits dug as the circumstance of the place permits, but there should not be more made than can be used, although we ought to make as much salt as we can sell. The depth of salt-pits should be moderate, and the bottom should be level, so that all the water is evaporated from the salt by the heat of the sun. The salt-pits should first be encrusted with salt, so that they may not suck up the water. The method of pouring or leading sea-water into salt-pits is very old, and is still in use in many places. The method is not less old, but less common, to pour well-water into salt-pits, as was done in Babylon, for which Pliny is the authority, and in Cappadocia, where they used not only well-water, but also spring-water. In all hot countries salt-water and lake-water are conducted, poured or carried into salt-pits, and, being dried by the heat of the sun, are converted into salt.[1] While the salt-water contained in the salt-pits is being heated by the sun, if they be flooded with great and frequent showers of rain the evaporation is hindered. If this happens rarely, the salt acquires a disagreeable[2] flavour, and in this case the salt-pits have to be filled with other sweet water. [Illustration 547 (Salt Pans): A--Sea. B--Pool. C--Gate. D--Trenches. E--Salt basins. F--Rake. G--Shovel.] Salt from sea-water is made in the following manner. Near that part of the seashore where there is a quiet pool, and there are wide, level plains which the inundations of the sea do not overflow, three, four, five, or six trenches are dug six feet wide, twelve feet deep, and six hundred feet long, or longer if the level place extends for a longer distance; they are two hundred feet distant from one another; between these are three transverse trenches. Then are dug the principal pits, so that when the water has been raised from the pool it can flow into the trenches, and from thence into the salt-pits, of which there are numbers on the level ground between the trenches. The salt-pits are basins dug to a moderate depth; these are banked round with the earth which was dug in sinking them or in cleansing them, so that between the basins, earth walls are made a foot high, which retain the water let into them. The trenches have openings, through which the first basins receive the water; these basins also have openings, through which the water flows again from one into the other. There should be a slight fall, so that the water may flow from one basin into the other, and can thus be replenished. All these things having been done rightly and in order, the gate is raised that opens the mouth of the pool which contains sea-water mixed with rain-water or river-water; and thus all of the trenches are filled. Then the gates of the first basins are opened, and thus the remaining basins are filled with the water from the first; when this salt-water condenses, all these basins are incrusted, and thus made clean from earthy matter. Then again the first basins are filled up from the nearest trench with the same kind of water, and left until much of the thin liquid is converted into vapour by the heat of the sun and dissipated, and the remainder is considerably thickened. Then their gates being opened, the water passes into the second basins; and when it has remained there for a certain space of time the gates are opened, so that it flows into the third basins, where it is all condensed into salt. After the salt has been taken out, the basins are filled again and again with sea-water. The salt is raked up with wooden rakes and thrown out with shovels. [Illustration 549 (Salt Wells): A--Shed. B--Painted signs. C--First room. D--Middle room. E--Third room. F--Two little windows in the end wall. G--Third little window in the roof. H--Well. I--Well of another kind. K--Cask. L--Pole. M--Forked sticks in which the porters rest the pole when they are tired.] Salt-water is also boiled in pans, placed in sheds near the wells from which it is drawn. Each shed is usually named from some animal or other thing which is pictured on a tablet nailed to it. The walls of these sheds are made either from baked earth or from wicker work covered with thick mud, although some may be made of stones or bricks. When of brick they are often sixteen feet high, and if the roof rises twenty-four feet high, then the walls which are at the ends must be made forty feet high, as likewise the interior partition walls. The roof consists of large shingles four feet long, one foot wide, and two digits thick; these are fixed on long narrow planks placed on the rafters, which are joined at the upper end and slope in opposite directions. The whole of the under side is plastered one digit thick with straw mixed with lute; likewise the roof on the outside is plastered one and a half feet thick with straw mixed with lute, in order that the shed should not run any risk of fire, and that it should be proof against rain, and be able to retain the heat necessary for drying the lumps of salt. Each shed is divided into three parts, in the first of which the firewood and straw are placed; in the middle room, separated from the first room by a partition, is the fireplace on which is placed the caldron. To the right of the caldron is a tub, into which is emptied the brine brought into the shed by the porters; to the left is a bench, on which there is room to lay thirty pieces of salt. In the third room, which is in the back part of the house, there is made a pile of clay or ashes eight feet higher than the floor, being the same height as the bench. The master and his assistants, when they carry away the lumps of salt from the caldrons, go from the former to the latter. They ascend from the right side of the caldron, not by steps, but by a slope of earth. At the top of the end wall are two small windows, and a third is in the roof, through which the smoke escapes. This smoke, emitted from both the back and the front of the furnace, finds outlet through a hood through which it makes its way up to the windows; this hood consists of boards projecting one beyond the other, which are supported by two small beams of the roof. Opposite the fireplace the middle partition has an open door eight feet high and four feet wide, through which there is a gentle draught which drives the smoke into the last room; the front wall also has a door of the same height and width. Both of these doors are large enough to permit the firewood or straw or the brine to be carried in, and the lumps of salt to be carried out; these doors must be closed when the wind blows, so that the boiling will not be hindered. Indeed, glass panes which exclude the wind but transmit the light, should be inserted in the windows in the walls. They construct the greater part of the fireplace of rock-salt and of clay mixed with salt and moistened with brine, for such walls are greatly hardened by the fire. These fireplaces are made eight and a half feet long, seven and three quarters feet wide, and, if wood is burned in them, nearly four feet high; but if straw is burned in them, they are six feet high. An iron rod, about four feet long, is engaged in a hole in an iron foot, which stands on the base of the middle of the furnace mouth. This mouth is three feet in width, and has a door which opens inward; through it they throw in the straw. [Illustration 551 (Salt Caldron): A--Fireplace. B--Mouth of fireplace. C--Caldron. D--Posts sunk into the ground. E--Cross-beams. F--Shorter bars. G--Iron hooks. H--Staples. I--Longer bars. K--Iron rod bent to support the caldron.] The caldrons are rectangular, eight feet long, seven feet wide, and half a foot high, and are made of sheets of iron or lead, three feet long and of the same width, all but two digits. These plates are not very thick, so that the water is heated more quickly by the fire, and is boiled away rapidly. The more salty the water is, the sooner it is condensed into salt. To prevent the brine from leaking out at the points where the metal plates are fastened with rivets, the caldrons are smeared over with a cement made of ox-liver and ox-blood mixed with ashes. On each side of the middle of the furnace two rectangular posts, three feet long, and half a foot thick and wide are set into the ground, so that they are distant from each other only one and a half feet. Each of them rises one and a half feet above the caldron. After the caldron has been placed on the walls of the furnace, two beams of the same width and thickness as the posts, but four feet long, are laid on these posts, and are mortised in so that they shall not fall. There rest transversely upon these beams three bars, three feet long, three digits wide, and two digits thick, distant from one another one foot. On each of these hang three iron hooks, two beyond the beams and one in the middle; these are a foot long, and are hooked at both ends, one hook turning to the right, the other to the left. The bottom hook catches in the eye of a staple, whose ends are fixed in the bottom of the caldron, and the eye projects from it. There are besides, two longer bars six feet long, one palm wide, and three digits thick, which pass under the front beam and rest upon the rear beam. At the rear end of each of the bars there is an iron hook two feet and three digits long, the lower end of which is bent so as to support the caldron. The rear end of the caldron does not rest on the two rear corners of the fireplace, but is distant from the fireplace two thirds of a foot, so that the flame and smoke can escape; this rear end of the fireplace is half a foot thick and half a foot higher than the caldron. This is also the thickness and height of the wall between the caldron and the third room of the shed, to which it is adjacent. This back wall is made of clay and ashes, unlike the others which are made of rock-salt. The caldron rests on the two front corners and sides of the fireplace, and is cemented with ashes, so that the flames shall not escape. If a dipperful of brine poured into the caldron should flow into all the corners, the caldron is rightly set upon the fireplace. The wooden dipper holds ten Roman _sextarii_, and the cask holds eight dippers full[3]. The brine drawn up from the well is poured into such casks and carried by porters, as I have said before, into the shed and poured into a tub, and in those places where the brine is very strong it is at once transferred with the dippers into the caldron. That brine which is less strong is thrown into a small tub with a deep ladle, the spoon and handle of which are hewn out of one piece of wood. In this tub rock-salt is placed in order that the water should be made more salty, and it is then run off through a launder which leads into the caldron. From thirty-seven dippersful of brine the master or his deputy, at Halle in Saxony,[4] makes two cone-shaped pieces of salt. Each master has a helper, or in the place of a helper his wife assists him in his work, and, in addition, a youth who throws wood or straw under the caldron. He, on account of the great heat of the workshop, wears a straw cap on his head and a breech cloth, being otherwise quite naked. As soon as the master has poured the first dipperful of brine into the caldron the youth sets fire to the wood and straw laid under it. If the firewood is bundles of faggots or brushwood, the salt will be white, but if straw is burned, then it is not infrequently blackish, for the sparks, which are drawn up with the smoke into the hood, fall down again into the water and colour it black. [Illustration 553 (Salt Caldron): A--Wooden dipper. B--Cask. C--Tub. D--Master. E--Youth. F--Wife. G--Wooden spade. H--Boards. I--Baskets. K--Hoe. L--Rake. M--Straw. N--Bowl. O--Bucket containing the blood. P--Tankard which contains beer.] In order to accelerate the condensation of the brine, when the master has poured in two casks and as many dippersful of brine, he adds about a Roman _cyathus_ and a half of bullock's blood, or of calf's blood, or buck's blood, or else he mixes it into the nineteenth dipperful of brine, in order that it may be dissolved and distributed into all the corners of the caldron; in other places the blood is dissolved in beer. When the boiling water seems to be mixed with scum, he skims it with a ladle; this scum, if he be working with rock-salt, he throws into the opening in the furnace through which the smoke escapes, and it is dried into rock-salt; if it be not from rock-salt, he pours it on to the floor of the workshop. From the beginning to the boiling and skimming is the work of half-an-hour; after this it boils down for another quarter-of-an-hour, after which time it begins to condense into salt. When it begins to thicken with the heat, he and his helper stir it assiduously with a wooden spatula, and then he allows it to boil for an hour. After this he pours in a _cyathus_ and a half of beer. In order that the wind should not blow into the caldron, the helper covers the front with a board seven and a half feet long and one foot high, and covers each of the sides with boards three and three quarters feet long. In order that the front board may hold more firmly, it is fitted into the caldron itself, and the side-boards are fixed on the front board and upon the transverse beam. Afterward, when the boards have been lifted off, the helper places two baskets, two feet high and as many wide at the top, and a palm wide at the bottom, on the transverse beams, and into them the master throws the salt with a shovel, taking half-an-hour to fill them. Then, replacing the boards on the caldron, he allows the brine to boil for three quarters of an hour. Afterward the salt has again to be removed with a shovel, and when the baskets are full, they pile up the salt in heaps. In different localities the salt is moulded into different shapes. In the baskets the salt assumes the form of a cone; it is not moulded in baskets alone, but also in moulds into which they throw the salt, which are made in the likeness of many objects, as for instance tablets. These tablets and cones are kept in the higher part of the third room of the house, or else on the flat bench of the same height, in order that they may dry better in the warm air. In the manner I have described, a master and his helper continue one after the other, alternately boiling the brine and moulding the salt, day and night, with the exception only of the annual feast days. No caldron is able to stand the fire for more than half a year. The master pours in water and washes it out every week; when it is washed out he puts straw under it and pounds it; new caldrons he washes three times in the first two weeks, and afterward twice. In this manner the incrustations fall from the bottom; if they are not cleared off, the salt would have to be made more slowly over a fiercer fire, which requires more brine and burns the plates of the caldron. If any cracks make their appearance in the caldron they are filled up with cement. The salt made during the first two weeks is not so good, being usually stained by the rust at the bottom where incrustations have not yet adhered. Although salt made in this manner is prepared only from the brine of springs and wells, yet it is also possible to use this method in the case of river-, lake-, and sea-water, and also of those waters which are artificially salted. For in places where rock-salt is dug, the impure and the broken pieces are thrown into fresh water, which, when boiled, condenses into salt. Some, indeed, boil sea-salt in fresh water again, and mould the salt into the little cones and other shapes. [Illustration 554 (Salt Boiling): A--Pool. B--Pots. C--Ladle. D--Pans. E--Tongs.] Some people make salt by another method, from salt water which flows from hot springs that issue boiling from the earth. They set earthenware pots in a pool of the spring-water, and into them they pour water scooped up with ladles from the hot spring until they are half full. The perpetual heat of the waters of the pool evaporates the salt water just as the heat of the fire does in the caldrons. As soon as it begins to thicken, which happens when it has been reduced by boiling to a third or more, they seize the pots with tongs and pour the contents into small rectangular iron pans, which have also been placed in the pool. The interior of these pans is usually three feet long, two feet wide, and three digits deep, and they stand on four heavy legs, so that the water flows freely all round, but not into them. Since the water flows continuously from the pool through the little canals, and the spring always provides a new and copious supply, always boiling hot, it condenses the thickened water poured into the pans into salt; this is at once taken out with shovels, and then the work begins all over again. If the salty water contains other juices, as is usually the case with hot springs, no salt should be made from them. [Illustration 555 (Salt Boiling): A--Pots. B--Tripod. C--Deep ladle.] Others boil salt water, and especially sea-water, in large iron pots; this salt is blackish, for in most cases they burn straw under them. Some people boil in these pots the brine in which fish is pickled. The salt which they make tastes and smells of fish. [Illustration 556 (Salt evaporated on faggots): A--Trench. B--Vat into which the salt water flows. C--Ladle. D--Small bucket with pole fastened into it.] Those who make salt by pouring brine over firewood, lay the wood in trenches which are twelve feet long, seven feet wide, and two and one half feet deep, so that the water poured in should not flow out. These trenches are constructed of rock-salt wherever it is to be had, in order that they should not soak up the water, and so that the earth should not fall in on the front, back and sides. As the charcoal is turned into salt at the same time as the salt liquor, the Spaniards think, as Pliny writes[5], that the wood itself turns into salt. Oak is the best wood, as its pure ash yields salt; elsewhere hazel-wood is lauded. But with whatever wood it be made, this salt is not greatly appreciated, being black and not quite pure; on that account this method of salt-making is disdained by the Germans and Spaniards. [Illustration 557 (Lye Making): A--Large vat. B--Plug. C--Small tub. D--Deep ladle. E--Small vat. F--Caldron.] The solutions from which salt is made are prepared from salty earth or from earth rich in salt and saltpetre. Lye is made from the ashes of reeds and rushes. The solution obtained from salty earth by boiling, makes salt only; from the other, of which I will speak more a little later, salt and saltpetre are made; and from ashes is derived lye, from which its own salt is obtained. The ashes, as well as the earth, should first be put into a large vat; then fresh water should be poured over the ashes or earth, and it should be stirred for about twelve hours with a stick, so that it may dissolve the salt. Then the plug is pulled out of the large vat; the solution of salt or the lye is drained into a small tub and emptied with ladles into small vats; finally, such a solution is transferred into iron or lead caldrons and boiled, until the water having evaporated, the juices are condensed into salt. The above are the various methods for making salt. (Illustration p. 557.) [Illustration 559 (Nitrum-pits): A--Nile. B--Nitrum-pits, such as I conjecture them to be.[7]] _Nitrum_[6] is usually made from _nitrous_ waters, or from solutions or from lye. In the same manner as sea-water or salt-water is poured into salt-pits and evaporated by the heat of the sun and changed into salt, so the _nitrous_ Nile is led into _nitrum_ pits and evaporated by the heat of the sun and converted into _nitrum_. Just as the sea, in flowing of its own will over the soil of this same Egypt, is changed into salt, so also the Nile, when it overflows in the dog days, is converted into _nitrum_ when it flows into the _nitrum_ pits. The solution from which _nitrum_ is produced is obtained from fresh water percolating through _nitrous_ earth, in the same manner as lye is made from fresh water percolating through ashes of oak or hard oak. Both solutions are taken out of vats and poured into rectangular copper caldrons, and are boiled until at last they condense into _nitrum_. [Illustration 561 (Soda Making): A--Vat in which the soda is mixed. B--Caldron. C--Tub in which _chrysocolla_ is condensed. D--Copper wires. E--Mortar.] Native as well as manufactured _nitrum_ is mixed in vats with urine and boiled in the same caldrons; the decoction is poured into vats in which are copper wires, and, adhering to them, it hardens and becomes _chrysocolla_, which the Moors call _borax_. Formerly _nitrum_ was compounded with Cyprian verdigris, and ground with Cyprian copper in Cyprian mortars, as Pliny writes. Some _chrysocolla_ is made of rock-alum and sal-ammoniac.[8] [Illustration 563 (Saltpetre Making): A--Caldron. B--Large vat into which sand is thrown. C--Plug. D--Tub. E--Vat containing the rods.] Saltpetre[9] is made from a dry, slightly fatty earth, which, if it be retained for a while in the mouth, has an acrid and salty taste. This earth, together with a powder, are alternately put into a vat in layers a palm deep. The powder consists of two parts of unslaked lime and three parts of ashes of oak, or holmoak, or Italian oak, or Turkey oak, or of some similar kind. Each vat is filled with alternate layers of these to within three-quarters of a foot of the top, and then water is poured in until it is full. As the water percolates through the material it dissolves the saltpetre; then, the plug being pulled out from the vat, the solution is drained into a tub and ladled out into small vats. If when tested it tastes very salty, and at the same time acrid, it is good; but, if not, then it is condemned, and it must be made to percolate again through the same material or through a fresh lot. Even two or three waters may be made to percolate through the same earth and become full of saltpetre, but the solutions thus obtained must not be mixed together unless all have the same taste, which rarely or never happens. The first of these solutions is poured into the first vat, the next into the second, the third into the third vat; the second and third solutions are used instead of plain water to percolate through fresh material; the first solution is made in this manner from both the second and third. As soon as there is an abundance of this solution it is poured into the rectangular copper caldron and evaporated to one half by boiling; then it is transferred into a vat covered with a lid, in which the earthy matter settles to the bottom. When the solution is clear it is poured back into the same pan, or into another, and re-boiled. When it bubbles and forms a scum, in order that it should not run over and that it may be greatly purified, there is poured into it three or four pounds of lye, made from three parts of oak or similar ash and one of unslaked lime. But in the water, prior to its being poured in, is dissolved rock-alum, in the proportion of one hundred and twenty _librae_ of the former to five _librae_ of the latter. Shortly afterward the solution will be found to be clear and blue. It is boiled until the waters, which are easily volatile (_subtiles_), are evaporated, and then the greater part of the salt, after it has settled at the bottom of the pan, is taken out with iron ladles. Then the concentrated solution is transferred to the vat in which rods are placed horizontally and vertically, to which it adheres when cold, and if there be much, it is condensed in three or four days into saltpetre. Then the solution which has not congealed, is poured out and put on one side or re-boiled. The saltpetre being cut out and washed with its own solution, is thrown on to boards that it may drain and dry. The yield of saltpetre will be much or little in proportion to whether the solution has absorbed much or little; when the saltpetre has been obtained from lye, which purifies itself, it is somewhat clear and pure. The purest and most transparent, because free from salt, is made if it is drawn off at the thickening stage, according to the following method. There are poured into the caldron the same number of _amphorae_ of the solution as of _congii_ of the lye of which I have already spoken, and into the same caldron is thrown as much of the already made saltpetre as the solution and lye will dissolve. As soon as the mixture effervesces and forms scum, it is transferred to a vat, into which on a cloth has been thrown washed sand obtained from a river. Soon afterward the plug is drawn out of the hole at the bottom, and the mixture, having percolated through the sand, escapes into a tub. It is then reduced by boiling in one or another of the caldrons, until the greater part of the solution has evaporated; but as soon as it is well boiled and forms scum, a little lye is poured into it. Then it is transferred to another vat in which there are small rods, to which it adheres and congeals in two days if there is but little of it, or if there is much in three days, or at the most in four days; if it does not condense, it is poured back into the caldron and re-boiled down to half; then it is transferred to the vat to cool. The process must be repeated as often as is necessary. Others refine saltpetre by another method, for with it they fill a pot made of copper, and, covering it with a copper lid, set it over live coals, where it is heated until it melts. They do not cement down the lid, but it has a handle, and can be lifted for them to see whether or not the melting has taken place. When it has melted, powdered sulphur is sprinkled in, and if the pot set on the fire does not light it, the sulphur kindles, whereby the thick, greasy matter floating on the saltpetre burns up, and when it is consumed the saltpetre is pure. Soon afterward the pot is removed from the fire, and later, when cold, the purest saltpetre is taken out, which has the appearance of white marble, the earthy residue then remains at the bottom. The earths from which the solution was made, together with branches of oak or similar trees, are exposed under the open sky and sprinkled with water containing saltpetre. After remaining thus for five or six years, they are again ready to be made into a solution. Pure saltpetre which has rested many years in the earth, and that which exudes from the stone walls of wine cellars and dark places, is mixed with the first solution and evaporated by boiling. Thus far I have described the methods of making _nitrum_, which are not less varied or multifarious than those for making salt. Now I propose to describe the methods of making alum,[10] which are likewise neither all alike, nor simple, because it is made from boiling aluminous water until it condenses to alum, or else from boiling a solution of alum which is obtained from a kind of earth, or from rocks, or from pyrites, or other minerals. [Illustration 567 (Vitriol Making): A--Tanks. B--Stirring poles. C--Plug. D--Trough. E--Reservoir. F--Launder. G--lead caldron. H--Wooden tubs sunk into the earth. I--Vats in which twigs are fixed.] This kind of earth having first been dug up in such quantity as would make three hundred wheelbarrow loads, is thrown into two tanks; then the water is turned into them, and if it (the earth) contains vitriol it must be diluted with urine. The workmen must many times a day stir the ore with long, thick sticks in order that the water and urine may be mixed with it; then the plugs having been taken out of both tanks, the solution is drawn off into a trough, which is carved out of one or two trees. If the locality is supplied with an abundance of such ore, it should not immediately be thrown into the tanks, but first conveyed into open spaces and heaped up, for the longer it is exposed to the air and the rain, the better it is; after some months, during which the ore has been heaped up in open spaces into mounds, there are generated veinlets of far better quality than the ore. Then it is conveyed into six or more tanks, nine feet in length and breadth and five in depth, and afterward water is drawn into them of similar solution. After this, when the water has absorbed the alum, the plugs are pulled out, and the solution escapes into a round reservoir forty feet wide and three feet deep. Then the ore is thrown out of the tanks into other tanks, and water again being run into the latter and the urine added and stirred by means of poles, the plugs are withdrawn and the solution is run off into the same reservoir. A few days afterward, the reservoirs containing the solution are emptied through a small launder, and run into rectangular lead caldrons; it is boiled in them until the greater part of the water has evaporated. The earthy sediment deposited at the bottom of the caldron is composed of fatty and aluminous matter, which usually consists of small incrustations, in which there is not infrequently found a very white and very light powder of asbestos or gypsum. The solution now seems to be full of meal. Some people instead pour the partly evaporated solution into a vat, so that it may become pure and clear; then pouring it back into the caldron, they boil it again until it becomes mealy. By whichever process it has been condensed, it is then poured into a wooden tub sunk into the earth in order to cool it. When it becomes cold it is poured into vats, in which are arranged horizontal and vertical twigs, to which the alum clings when it condenses; and thus are made the small white transparent cubes, which are laid to dry in hot rooms. If vitriol forms part of the aluminous ore, the material is dissolved in water without being mixed with urine, but it is necessary to pour that into the clear and pure solution when it is to be re-boiled. This separates the vitriol from the alum, for by this method the latter sinks to the bottom of the caldron, while the former floats on the top; both must be poured separately into smaller vessels, and from these into vats to condense. If, however, when the solution was re-boiled they did not separate, then they must be poured from the smaller vessels into larger vessels and covered over; then the vitriol separating from the alum, it condenses. Both are cut out and put to dry in the hot room, and are ready to be sold; the solution which did not congeal in the vessels and vats is again poured back into the caldron to be re-boiled. The earth which settled at the bottom of the caldron is carried back to the tanks, and, together with the ore, is again dissolved with water and urine. The earth which remains in the tanks after the solution has been drawn off is emptied in a heap, and daily becomes more and more aluminous in the same way as the earth from which saltpetre was made, but fuller of its juices, wherefore it is again thrown into the tanks and percolated by water. [Illustration 571 (Alum Making): A--Furnace. B--Enclosed space. C--Aluminous rock. D--Deep ladle. E--Caldron. F--Launder. G--Troughs.] Aluminous rock is first roasted in a furnace similar to a lime kiln. At the bottom of the kiln a vaulted fireplace is made of the same kind of rock; the remainder of the empty part of the kiln is then entirely filled with the same aluminous rocks. Then they are heated with fire until they are red hot and have exhaled their sulphurous fumes, which occurs, according to their divers nature, within the space of ten, eleven, twelve, or more hours. One thing the master must guard against most of all is not to roast the rock either too much or too little, for on the one hand they would not soften when sprinkled with water, and on the other they either would be too hard or would crumble into ashes; from neither would much alum be obtained, for the strength which they have would be decreased. When the rocks are cooled they are drawn out and conveyed into an open space, where they are piled one upon the other in heaps fifty feet long, eight feet wide, and four feet high, which are sprinkled for forty days with water carried in deep ladles. In spring the sprinkling is done both morning and evening, and in summer at noon besides. After being moistened for this length of time the rocks begin to fall to pieces like slaked lime, and there originates a certain new material of the future alum, which is soft and similar to the _liquidae medullae_ found in the rocks. It is white if the stone was white before it was roasted, and rose-coloured if red was mixed with the white; from the former, white alum is obtained, and from the latter, rose-coloured. A round furnace is made, the lower part of which, in order to be able to endure the force of the heat, is made of rock that neither melts nor crumbles to powder by the fire. It is constructed in the form of a basket, the walls of which are two feet high, made of the same rock. On these walls rests a large round caldron made of copper plates, which is concave at the bottom, where it is eight feet in diameter. In the empty space under the bottom they place the wood to be kindled with fire. Around the edge of the bottom of the caldron, rock is built in cone-shaped, and the diameter of the bottom of the rock structure is seven feet, and of the top ten feet; it is eight feet deep. The inside, after being rubbed over with oil, is covered with cement, so that it may be able to hold boiling water; the cement is composed of fresh lime, of which the lumps are slaked with wine, of iron-scales, and of sea-snails, ground and mixed with the white of eggs and oil. The edges of the caldron are surmounted with a circle of wood a foot thick and half a foot high, on which the workmen rest the wooden shovels with which they cleanse the water of earth and of the undissolved lumps of rock that remain at the bottom of the caldron. The caldron, being thus prepared, is entirely filled through a launder with water, and this is boiled with a fierce fire until it bubbles. Then little by little eight wheelbarrow loads of the material, composed of roasted rock moistened with water, are gradually emptied into the caldron by four workmen, who, with their shovels which reach to the bottom, keep the material stirred and mixed with water, and by the same means they lift the lumps of undissolved rock out of the caldron. In this manner the material is thrown in, in three or four lots, at intervals of two or three hours more or less; during these intervals, the water, which has been cooled by the rock and material, again begins to boil. The water, when sufficiently purified and ready to congeal, is ladled out and run off with launders into thirty troughs. These troughs are made of oak, holm oak, or Turkey oak; their interior is six feet long, five feet deep, and four feet wide. In these the water congeals and condenses into alum, in the spring in the space of four days, and in summer in six days. Afterward the holes at the bottom of the oak troughs being opened, the water which has not congealed is drawn off into buckets and poured back into the caldron; or it may be preserved in empty troughs, so that the master of the workmen, having seen it, may order his helpers to pour it into the caldron, for the water which is not altogether wanting in alum, is considered better than that which has none at all. Then the alum is hewn out with a knife or a chisel. It is thick and excellent according to the strength of the rock, either white or pink according to the colour of the rock. The earthy powder, which remains three to four digits thick as the residue of the alum at the bottom of the trough is again thrown into the caldron and boiled with fresh aluminous material. Lastly, the alum cut out is washed, and dried, and sold. Alum is also made from crude pyrites and other aluminous mixtures. It is first roasted in an enclosed area; then, after being exposed for some months to the air in order to soften it, it is thrown into vats and dissolved. After this the solution is poured into the leaden rectangular pans and boiled until it condenses into alum. The pyrites and other stones which are not mixed with alum alone, but which also contain vitriol, as is most usually the case, are both treated in the manner which I have already described. Finally, if metal is contained in the pyrites and other rock, this material must be dried, and from it either gold, silver, or copper is made in a furnace. Vitriol[11] can be made by four different methods; by two of these methods from water containing vitriol; by one method from a solution of _melanteria_, _sory_ and _chalcitis_; and by another method from earth or stones mixed with vitriol. [Illustration 574 (Vitriol Making): A--Tunnel. B--Bucket. C--Pit.] The vitriol water is collected into pools, and if it cannot be drained into them, it must be drawn up and carried to them in buckets by a workman. In hot regions or in summer, it is poured into out-of-door pits which have been dug to a certain depth, or else it is extracted from shafts by pumps and poured into launders, through which it flows into the pits, where it is condensed by the heat of the sun. In cold regions and in winter these vitriol waters are boiled down with equal parts of fresh water in rectangular leaden caldrons; then, when cold, the mixture is poured into vats or into tanks, which Pliny calls wooden fish-tanks. In these tanks light cross-beams are fixed to the upper part, so that they may be stationary, and from them hang ropes stretched with little stones; to these the contents of the thickened solutions congeal and adhere in transparent cubes or seeds of vitriol, like bunches of grapes. [Illustration 575 (Vitriol Making): A--Caldron. B--Tank. C--Cross-bars. D--Ropes. E--Little stones.] By the third method vitriol is made out of _melanteria_ and _sory_. If the mines give an abundant supply of _melanteria_ and _sory_, it is better to reject the _chalcitis_, and especially the _misy_, for from these the vitriol is impure, particularly from the _misy_. These materials having been dug and thrown into the tanks, they are first dissolved with water; then, in order to recover the pyrites from which copper is not rarely smelted and which forms a sediment at the bottom of the tanks, the solution is transferred to other vats, which are nine feet wide and three feet deep. Twigs and wood which float on the surface are lifted out with a broom made of twigs, and afterward all the sediment settles at the bottom of this vat. The solution is poured into a rectangular leaden caldron eight feet long, three feet wide, and the same in depth. In this caldron it is boiled until it becomes thick and viscous, when it is poured into a launder, through which it runs into another leaden caldron of the same size as the one described before. When cold, the solution is drawn off through twelve little launders, out of which it flows into as many wooden tubs four and a half feet deep and three feet wide. Upon these tubs are placed perforated crossbars distant from each other from four to six digits, and from the holes hang thin laths, which reach to the bottom, with pegs or wedges driven into them. The vitriol adheres to these laths, and within the space of a few days congeals into cubes, which are taken away and put into a chamber having a sloping board floor, so that the moisture which drips from the vitriol may flow into a tub beneath. This solution is re-boiled, as is also that solution which was left in the twelve tubs, for, by reason of its having become too thin and liquid, it did not congeal, and was thus not converted into vitriol. [Illustration 576 (Vitriol Making): A--Wooden tub. B--Cross-bars. C--Laths. D--Sloping floor of the chamber. E--Tub placed under it.] [Illustration 577 (Vitriol Making): A--Caldron. B--Moulds. C--Cakes.] The fourth method of making vitriol is from vitriolous earth or stones. Such ore is at first carried and heaped up, and is then left for five or six months exposed to the rain of spring and autumn, to the heat of summer, and to the rime and frost of winter. It must be turned over several times with shovels, so that the part at the bottom may be brought to the top, and it is thus ventilated and cooled; by this means the earth crumbles up and loosens, and the stone changes from hard to soft. Then the ore is covered with a roof, or else it is taken away and placed under a roof, and remains in that place six, seven, or eight months. Afterward as large a portion as is required is thrown into a vat, which is half-filled with water; this vat is one hundred feet long, twenty-four feet wide, eight feet deep. It has an opening at the bottom, so that when it is opened the dregs of the ore from which the vitriol comes may be drawn off, and it has, at the height of one foot from the bottom, three or four little holes, so that, when closed, the water may be retained, and when opened the solution flows out. Thus the ore is mixed with water, stirred with poles and left in the tank until the earthy portions sink to the bottom and the water absorbs the juices. Then the little holes are opened, the solution flows out of the vat, and is caught in a vat below it; this vat is of the same length as the other, but twelve feet wide and four feet deep. If the solution is not sufficiently vitriolous it is mixed with fresh ore; but if it contains enough vitriol, and yet has not exhausted all of the ore rich in vitriol, it is well to dissolve the ore again with fresh water. As soon as the solution becomes clear, it is poured into the rectangular leaden caldron through launders, and is boiled until the water is evaporated. Afterward as many thin strips of iron as the nature of the solution requires, are thrown in, and then it is boiled again until it is thick enough, when cold, to congeal into vitriol. Then it is poured into tanks or vats, or any other receptacle, in which all of it that is apt to congeal does so within two or three days. The solution which does not congeal is either poured back into the caldron to be boiled again, or it is put aside for dissolving the new ore, for it is far preferable to fresh water. The solidified vitriol is hewn out, and having once more been thrown into the caldron, is re-heated until it liquefies; when liquid, it is poured into moulds that it may be made into cakes. If the solution first poured out is not satisfactorily thickened, it is condensed two or three times, and each time liquefied in the caldron and re-poured into the moulds, in which manner pure cakes, beautiful to look at, are made from it. The vitriolous pyrites, which are to be numbered among the mixtures (_mistura_), are roasted as in the case of alum, and dissolved with water, and the solution is boiled in leaden caldrons until it condenses into vitriol. Both alum and vitriol are often made out of these, and it is no wonder, for these juices are cognate, and only differ in the one point,--that the former is less, the latter more, earthy. That pyrites which contains metal must be smelted in the furnace. In the same manner, from other mixtures of vitriolic and metalliferous material are made vitriol and metal. Indeed, if ores of vitriolous pyrites abound, the miners split small logs down the centre and cut them off in lengths as long as the drifts and tunnels are wide, in which they lay them down transversely; but, that they may be stable, they are laid on the ground with the wide side down and the round side up, and they touch each other at the bottom, but not at the top. The intermediate space is filled with pyrites, and the same crushed are scattered over the wood, so that, coming in or going out, the road is flat and even. Since the drifts or tunnels drip with water, these pyrites are soaked, and from them are freed the vitriol and cognate things. If the water ceases to drip, these dry and harden, and then they are raised from the shafts, together with the pyrites not yet dissolved in the water, or they are carried out from the tunnels; then they are thrown into vats or tanks, and boiling water having been poured over them, the vitriol is freed and the pyrites are dissolved. This green solution is transferred to other vats or tanks, that it may be made clear and pure; it is then boiled in the lead caldrons until it thickens; afterward it is poured into wooden tubs, where it condenses on rods, or reeds, or twigs, into green vitriol. Sulphur is made from sulphurous waters, from sulphurous ores, and from sulphurous mixtures. These waters are poured into the leaden caldrons and boiled until they condense into sulphur. From this latter, heated together with iron-scales, and transferred into pots, which are afterward covered with lute and refined sulphur, another sulphur is made, which we call _caballinum_.[12] [Illustration 579 (Sulphur Making): A--Pots having spouts. B--Pots without spouts. C--Lids.] The ores[13] which consist mostly of sulphur and of earth, and rarely of other minerals, are melted in big-bellied earthenware pots. The furnaces, which hold two of these pots, are divided into three parts; the lowest part is a foot high, and has an opening at the front for the draught; the top of this is covered with iron plates, which are perforated near the edges, and these support iron rods, upon which the firewood is placed. The middle part of the furnace is one and a half feet high, and has a mouth in front, so that the wood may be inserted; the top of this has rods, upon which the bottom of the pots stand. The upper part is about two feet high, and the pots are also two feet high and one digit thick; these have below their mouths a long, slender spout. In order that the mouth of the pot may be covered, an earthenware lid is made which fits into it. For every two of these pots there must be one pot of the same size and shape, and without a spout, but having three holes, two of which are below the mouth and receive the spouts of the two first pots; the third hole is on the opposite side at the bottom, and through it the sulphur flows out. In each furnace are placed two pots with spouts, and the furnace must be covered by plates of iron smeared over with lute two digits thick; it is thus entirely closed in, but for two or three vent-holes through which the mouths of the pots project. Outside of the furnace, against one side, is placed the pot without a spout, into the two holes of which the two spouts of the other pots penetrate, and this pot should be built in at both sides to keep it steady. When the sulphur ore has been placed in the pots, and these placed in the furnace, they are closely covered, and it is desirable to smear the joint over with lute, so that the sulphur will not exhale, and for the same reason the pot below is covered with a lid, which is also smeared with lute. The wood having been kindled, the ores are heated until the sulphur is exhaled, and the vapour, arising through the spout, penetrates into the lower pot and thickens into sulphur, which falls to the bottom like melted wax. It then flows out through the hole, which, as I said, is at the bottom of this pot; and the workman makes it into cakes, or thin sticks or thin pieces of wood are dipped in it. Then he takes the burning wood and glowing charcoal from the furnace, and when it has cooled, he opens the two pots, empties the residues, which, if the ores were composed of sulphur and earth, resemble naturally extinguished ashes; but if the ores consisted of sulphur and earth and stone, or sulphur and stone only, they resemble earth completely dried or stones well roasted. Afterward the pots are re-filled with ore, and the whole work is repeated. [Illustration 581 (Sulphur Making): A--Long wall. B--High walls. C--Low walls. D--Plates. E--Upper pots. F--Lower pots.] The sulphurous mixture, whether it consists of stone and sulphur only, or of stone and sulphur and metal, may be heated in similar pots, but with perforated bottoms. Before the furnace is constructed, against the "second" wall of the works two lateral partitions are built seven feet high, three feet long, one and a half feet thick, and these are distant from each other twenty-seven feet. Between them are seven low brick walls, that measure but two feet and the same number of digits in height, and, like the other walls, are three feet long and one foot thick; these little walls are at equal distances from one another, consequently they will be two and one half feet apart. At the top, iron bars are fixed into them, which sustain iron plates three feet long and wide and one digit thick, so that they can bear not only the weight of the pots, but also the fierceness of the fire. These plates have in the middle a round hole one and a half digits wide; there must not be more than eight of these, and upon them as many pots are placed. These pots are perforated at the bottom, and the same number of whole pots are placed underneath them; the former contain the mixture, and are covered with lids; the latter contain water, and their mouths are under the holes in the plates. After wood has been arranged round the upper pots and ignited, the mixture being heated, red, yellow, or green sulphur drips from it and flows down through the hole, and is caught by the pots placed underneath the plates, and is at once cooled by the water. If the mixture contains metal, it is reserved for smelting, and, if not, it is thrown away. The sulphur from such a mixture can best be extracted if the upper pots are placed in a vaulted furnace, like those which I described among other metallurgical subjects in Book VIII., which has no floor, but a grate inside; under this the lower pots are placed in the same manner, but the plates must have larger holes. [Illustration 582 (Bitumen Making): A--Lower pot. B--Upper pot. C--Lid.] Others bury a pot in the ground, and place over it another pot with a hole at the bottom, in which pyrites or _cadmia_, or other sulphurous stones are so enclosed that the sulphur cannot exhale. A fierce fire heats the sulphur, and it drips away and flows down into the lower pot, which contains water. (Illustration p. 582). [Illustration 583 (Bitumen Making): A--Bituminous spring. B--Bucket. C--Pot. D--Lid.] Bitumen[14] is made from bituminous waters, from liquid bitumen, and from mixtures of bituminous substances. The water, bituminous as well as salty, at Babylon, as Pliny writes, was taken from the wells to the salt works and heated by the great heat of the sun, and condensed partly into liquid bitumen and partly into salt. The bitumen being lighter, floats on the top, while the salt being heavier, sinks to the bottom. Liquid bitumen, if there is much floating on springs, streams and rivers, is drawn up in buckets or other vessels; but, if there is little, it is collected with goose wings, pieces of linen, _ralla_, shreds of reeds, and other things to which it easily adheres, and it is boiled in large brass or iron pots by fire and condensed. As this bitumen is put to divers uses, some mix pitch with the liquid, others old cart-grease, in order to temper its viscosity; these, however long they are boiled in the pots, cannot be made hard. The mixtures containing bitumen are also treated in the same manner as those containing sulphur, in pots having a hole in the bottom, and it is rare that such bitumen is not highly esteemed. [Illustration 585 (Chrysocolla Making): A--Mouth of the tunnel. B--Trough. C--Tanks. D--Little trough.] Since all solidified juices and earths, if abundantly and copiously mixed with the water, are deposited in the beds of springs, streams or rivers, and the stones therein are coated by them, they do not require the heat of the sun or fire to harden them. This having been pondered over by wise men, they discovered methods by which the remainder of these solidified juices and unusual earths can be collected. Such waters, whether flowing from springs or tunnels, are collected in many wooden tubs or tanks arranged in consecutive order, and deposit in them such juices or earths; these being scraped off every year, are collected, as _chrysocolla_[15] in the Carpathians and as ochre in the Harz. There remains glass, the preparation of which belongs here, for the reason that it is obtained by the power of fire and subtle art from certain solidified juices and from coarse or fine sand. It is transparent, as are certain solidified juices, gems, and stones; and can be melted like fusible stones and metals. First I must speak of the materials from which glass is made; then of the furnaces in which it is melted; then of the methods by which it is produced. It is made from fusible stones and from solidified juices, or from other juicy substances which are connected by a natural relationship. Stones which are fusible, if they are white and translucent, are more excellent than the others, for which reason crystals take the first place. From these, when pounded, the most excellent transparent glass was made in India, with which no other could be compared, as Pliny relates. The second place is accorded to stones which, although not so hard as crystal, are yet just as white and transparent. The third is given to white stones, which are not transparent. It is necessary, however, first of all to heat all these, and afterward they are subjected to the pestle in order to break and crush them into coarse sand, and then they are passed through a sieve. If this kind of coarse or fine sand is found by the glass-makers near the mouth of a river, it saves them much labour in burning and crushing. As regards the solidified juices, the first place is given to soda; the second to white and translucent rock-salt; the third to salts which are made from lye, from the ashes of the musk ivy, or from other salty herbs. Yet there are some who give to this latter, and not to the former, the second place. One part of coarse or fine sand made from fusible stones should be mixed with two parts of soda or of rock-salt or of herb salts, to which are added minute particles of _magnes_.[16] It is true that in our day, as much as in ancient times, there exists the belief in the singular power of the latter to attract to itself the vitreous liquid just as it does iron, and by attracting it to purify and transform green or yellow into white; and afterward fire consumes the _magnes_. When the said juices are not to be had, two parts of the ashes of oak or holmoak, or of hard oak or Turkey oak, or if these be not available, of beech or pine, are mixed with one part of coarse or fine sand, and a small quantity of salt is added, made from salt water or sea-water, and a small particle of _magnes_; but these make a less white and translucent glass. The ashes should be made from old trees, of which the trunk at a height of six feet is hollowed out and fire is put in, and thus the whole tree is consumed and converted into ashes. This is done in winter when the snow lies long, or in summer when it does not rain, for the showers at other times of the year, by mixing the ashes with earth, render them impure; for this reason, at such times, these same trees are cut up into many pieces and burned under cover, and are thus converted into ashes. [Illustration 587 (Glass-making Furnace): A--Lower chamber of the first furnace. B--Upper chamber. C--Vitreous mass.] Some glass-makers use three furnaces, others two, others only one. Those who use three, melt the material in the first, re-melt it in the second, and in the third they cool the glowing glass vessels and other articles. Of these the first furnace must be vaulted and similar to an oven. In the upper chamber, which is six feet long, four feet wide, and two feet high, the mixed materials are heated by a fierce fire of dry wood until they melt and are converted into a vitreous mass. And if they are not satisfactorily purified from dross, they are taken out and cooled and broken into pieces; and the vitreous pieces are heated in pots in the same furnace. [Illustration 588 (Glass-making Furnace): A--Arches of the second furnace. B--Mouth of the lower chamber. C--Windows of the upper chamber. D--Big-bellied pots. E--Mouth of the third furnace. F--Recesses for the receptacles. G--Openings in the upper chamber. H--Oblong receptacles.] The second furnace is round, ten feet in diameter and eight feet high, and on the outside, so that it may be stronger, it is encompassed by five arches, one and one half feet thick; it consists in like manner of two chambers, of which the lower one is vaulted and is one and one half feet thick. In front this chamber has a narrow mouth, through which the wood can be put into the hearth, which is on the ground. At the top and in the middle of its vault, there is a large round hole which opens to the upper chamber, so that the flames can penetrate into it. Between the arches in the walls of the upper chamber are eight windows, so large that the big-bellied pots may be placed through them on to the floor of the chamber, around the large hole. The thickness of these pots is about two digits, their height the same number of feet, and the diameter of the belly one and a half feet, and of the mouth and bottom one foot. In the back part of the furnace is a rectangular hole, measuring in height and width a palm, through which the heat penetrates into a third furnace which adjoins it. This third furnace is rectangular, eight feet long and six feet wide; it also consists of two chambers, of which the lower has a mouth in front, so that firewood may be placed on the hearth which is on the ground. On each side of this opening in the wall of the lower chamber is a recess for oblong earthenware receptacles, which are about four feet long, two feet high, and one and a half feet wide. The upper chamber has two holes, one on the right side, the other on the left, of such height and width that earthenware receptacles may be conveniently placed in them. These latter receptacles are three feet long, one and a half feet high, the lower part one foot wide, and the upper part rounded. In these receptacles the glass articles, which have been blown, are placed so that they may cool in a milder temperature; if they were not cooled slowly they would burst asunder. When the vessels are taken from the upper chamber, they are immediately placed in the receptacles to cool. [Illustration 589 (Glass-making Furnaces): A--Lower chamber of the other second furnace. B--Middle one. C--Upper one. D--Its opening. E--Round opening. F--Rectangular opening.] Some who use two furnaces partly melt the mixture in the first, and not only re-melt it in the second, but also replace the glass articles there. Others partly melt and re-melt the material in different chambers of the second furnace. Thus the former lack the third furnace, and the latter, the first. But this kind of second furnace differs from the other second furnace, for it is, indeed, round, but the interior is eight feet in diameter and twelve feet high, and it consists of three chambers, of which the lowest is not unlike the lowest of the other second furnace. In the middle chamber wall there are six arched openings, in which are placed the pots to be heated, and the remainder of the small windows are blocked up with lute. In the middle top of the middle chamber is a square opening a palm in length and width. Through this the heat penetrates into the upper chamber, of which the rear part has an opening to receive the oblong earthenware receptacles, in which are placed the glass articles to be slowly cooled. On this side, the ground of the workshop is higher, or else a bench is placed there, so that the glass-makers may stand upon it to stow away their products more conveniently. Those who lack the first furnace in the evening, when they have accomplished their day's work, place the material in the pots, so that the heat during the night may melt it and turn it into glass. Two boys alternately, during night and day, keep up the fire by throwing dry wood on to the hearth. Those who have but one furnace use the second sort, made with three chambers. Then in the evening they pour the material into the pots, and in the morning, having extracted the fused material, they make the glass objects, which they place in the upper chamber, as do the others. The second furnace consists either of two or three chambers, the first of which is made of unburnt bricks dried in the sun. These bricks are made of a kind of clay that cannot be easily melted by fire nor resolved into powder; this clay is cleaned of small stones and beaten with rods. The bricks are laid with the same kind of clay instead of lime. From the same clay the potters also make their vessels and pots, which they dry in the shade. These two parts having been completed, there remains the third. [Illustration 591 (Glass Making): A--Blow-pipe. B--Little window. C--Marble. D--Forceps. E--Moulds by means of which the shapes are produced.] The vitreous mass having been made in the first furnace in the manner I described, is broken up, and the assistant heats the second furnace, in order that the fragments may be re-melted. In the meantime, while they are doing this, the pots are first warmed by a slow fire in the first furnace, so that the vapours may evaporate, and then by a fiercer fire, so that they become red in drying. Afterward the glass-makers open the mouth of the furnace, and, seizing the pots with tongs, if they have not cracked and fallen to pieces, quickly place them in the second furnace, and they fill them up with the fragments of the heated vitreous mass or with glass. Afterward they close up all the windows with lute and bricks, with the exception that in each there are two little windows left free; through one of these they inspect the glass contained in the pot, and take it up by means of a blow-pipe; in the other they rest another blow-pipe, so that it may get warm. Whether it is made of brass, bronze, or iron, the blow-pipe must be three feet long. In front of the window is inserted a lip of marble, on which rests the heaped-up clay and the iron shield. The clay holds the blow-pipe when it is put into the furnace, whereas the shield preserves the eyes of the glass-maker from the fire. All this having been carried out in order, the glass-makers bring the work to completion. The broken pieces they re-melt with dry wood, which emits no smoke, but only a flame. The longer they re-melt it, the purer and more transparent it becomes, the fewer spots and blisters there are, and therefore the glass-makers can carry out their work more easily. For this reason those who only melt the material from which glass is made for one night, and then immediately make it up into glass articles, make them less pure and transparent than those who first produce a vitreous mass and then re-melt the broken pieces again for a day and a night. And, again, these make a less pure and transparent glass than do those who melt it again for two days and two nights, for the excellence of the glass does not consist solely in the material from which it is made, but also in the melting. The glass-makers often test the glass by drawing it up with the blowpipes; as soon as they observe that the fragments have been re-melted and purified satisfactorily, each of them with another blow-pipe which is in the pot, slowly stirs and takes up the glass which sticks to it in the shape of a ball like a glutinous, coagulated gum. He takes up just as much as he needs to complete the article he wishes to make; then he presses it against the lip of marble and kneads it round and round until it consolidates. When he blows through the pipe he blows as he would if inflating a bubble; he blows into the blow-pipe as often as it is necessary, removing it from his mouth to re-fill his cheeks, so that his breath does not draw the flames into his mouth. Then, twisting the lifted blow-pipe round his head in a circle, he makes a long glass, or moulds the same in a hollow copper mould, turning it round and round, then warming it again, blowing it and pressing it, he widens it into the shape of a cup or vessel, or of any other object he has in mind. Then he again presses this against the marble to flatten the bottom, which he moulds in the interior with his other blow-pipe. Afterward he cuts out the lip with shears, and, if necessary, adds feet and handles. If it so please him, he gilds it and paints it with various colours. Finally, he lays it in the oblong earthenware receptacle, which is placed in the third furnace, or in the upper chamber of the second furnace, that it may cool. When this receptacle is full of other slowly-cooled articles, he passes a wide iron bar under it, and, carrying it on the left arm, places it in another recess. The glass-makers make divers things, such as goblets, cups, ewers, flasks, dishes, plates, panes of glass, animals, trees, and ships, all of which excellent and wonderful works I have seen when I spent two whole years in Venice some time ago. Especially at the time of the Feast of the Ascension they were on sale at Morano, where are located the most celebrated glass-works. These I saw on other occasions, and when, for a certain reason, I visited Andrea Naugerio in his house which he had there, and conversed with him and Francisco Asulano. END OF BOOK XII. FOOTNOTES: [1] The history of salt-making in salt-pans, from sea-water or salt springs, goes further back than human records. From an historical point of view the real interest attached to salt lies in the bearing which localities rich in either natural salt or salt springs, have had upon the movements of the human race. Many ancient trade routes have been due to them, and innumerable battles have been fought for their possession. Salt has at times served for currency, and during many centuries in nearly every country has served as a basis of taxation. These subjects do not, however, come within the scope of this text. For the quotation from Pliny referred to, see Note 14 below, on bitumen. [2] The first edition gives _graviorem_, the latter editions _gratiorem_, which latter would have quite the reverse meaning from the above. [3] The following are approximately the English equivalents:-- Pints. Quarts. Gallons. 1 _Cyathus_ .08 3 _Cyathi_ = 1 _Quartarius_ .24 4 _Quartarii_ = 1 _Sextarius_ .99 6 _Sextarii_ = 1 _Congius_ 5.94 2.97 16 _Sextarii_ = 1 _Modius_ 15.85 7.93 1.98 8 _Congii_ = 1 _Amphora_ 47.57 23.78 5.94 The dipper mentioned would thus hold about one and one quarter gallons, and the cask ten gallons. [4] The salt industry, founded upon salt springs, is still of importance to this city. It was a salt centre of importance to the Germanic tribes before Charles, the son of Charlemagne, erected a fortress here in 806. Mention of the salt works is made in the charter by Otto I., conveying the place to the Diocese of Magdeburg, in 968. [5] Pliny XXXI., 39-40. "In the Gallic provinces in Germany they pour salt water upon burning wood. The Spaniards in a certain place draw the brine from wells, which they call _Muria_. They indeed think that the wood turns to salt, and that the oak is the best, being the kind which is itself salty. Elsewhere the hazel is praised. Thus the charcoal even is turned into salt when it is steeped in brine. Whenever salt is made with wood it is black." [6] We have elsewhere in this book used the word "soda" for the Latin term _nitrum_, because we believe as used by Agricola it was always soda, and because some confusion of this term with its modern adaptation for saltpetre (nitre) might arise in the mind of the reader. Fortunately, Agricola usually carefully mentions other alkalis, such as the product from lixiviation of ashes, separately from his _nitrum_. In these paragraphs, however, he has soda and potash hopelessly mixed, wherefore we have here introduced the Latin term. The actual difference between potash and soda--the _nitrum_ of the Ancients, and the _alkali_ of Geber (and the glossary of Agricola), was not understood for two hundred years after Agricola, when Duhamel made his well-known determinations; and the isolation of sodium and potassium was, of course, still later by fifty years. If the reeds and rushes described in this paragraph grew near the sea, the salt from lixiviation would be soda, and likewise the Egyptian product was soda, but the lixiviation of wood-ash produces only potash; as seen above, all are termed _nitrum_ except the first. HISTORICAL NOTES.--The word _nitrum_, _nitron_, _nitri_, _neter_, _nether_, or similar forms, occurs in innumerable ancient writings. Among such references are Jeremiah (II., 22) Proverbs (XXV., 20), Herodotus (II., 86, 87), Aristotle (_Prob._ I., 39, _De Mirab._ 54), Theophrastus (_De Igne_ 435 ed. Heinsii, Hist. Plants III., 9), Dioscorides (V., 89), Pliny (XIV., 26, and XXXI., 46). A review of disputations on what salts this term comprised among the Ancients would itself fill a volume, but from the properties named it was no doubt mostly soda, more rarely potash, and sometimes both mixed with common salt. There is every reason to believe from the properties and uses mentioned, that it did not generally comprise nitre (saltpetre)--into which superficial error the nomenclature has led many translators. The preparation by way of burning, and the use of _nitrum_ for purposes for which we now use soap, for making glass, for medicines, cosmetics, salves, painting, in baking powder, for preserving food, embalming, etc., and the descriptions of its taste in "nitrous" waters,--all answer for soda and potash, but not for saltpetre. It is possible that the common occurrence of saltpetre as an efflorescence on walls might naturally lead to its use, but in any event its distinguishing characteristics are nowhere mentioned. As sal-ammoniac occurred in the volcanoes in Italy, it also may have been included in the _nitrum_ mentioned. _Nitrum_ was in the main exported from Egypt, but Theophrastus mentions its production from wood-ash, and Pliny very rightly states that burned lees of wine (argol) had the nature of _nitrum_. Many of the ancient writers understood that it was rendered more caustic by burning, and still more so by treatment with lime. According to Beckmann (Hist. of Inventions II., p. 488), the form of the word _natron_ was first introduced into Europe by two travellers in Egypt, Peter Ballon and Prosper Alpinus, about 1550. The word was introduced into mineralogy by Linnaeus in 1736. In the first instance _natron_ was applied to soda and potash in distinction to _nitre_ for saltpetre, and later _natron_ was applied solely to soda. It is desirable to mention here two other forms of soda and potash which are frequently mentioned by Agricola. "Ashes which wool dyers use" (_cineres quo infectores lanarum utuntur_).--There is no indication in any of Agricola's works as to whether this was some special wood-ash or whether it was the calcined residues from wool washing. The "yolk" or "suint" of wool, originating from the perspiration of the animal, has long been a source of crude potash. The water, after washing the wool, is evaporated, and the residue calcined. It contains about 85% K_{2}CO_{3}, the remainder being sodium and potassium sulphates. Another reason for assuming that it was not a wood-ash product, is that these products are separately mentioned. In either event, whether obtained from wool residues or from lixiviation of wood-ash, it would be an impure potash. In some methods of wool dyeing, a wash of soda was first given, so that it is barely possible that this substance was sodium carbonate. "Salt made from the ashes of musk ivy" (_sal ex anthyllidis cinere factus_,--Glossary, _salalkali_). This would be largely potash. [7] This wondrous illustration of soda-making from Nile water is no doubt founded upon Pliny (XXXI., 46). "It is made in almost the same manner as salt, except that sea-water is put into salt pans, whereas in the nitrous pans it is water of the Nile; these, with the subsidence of the Nile during the forty days, are impregnated with _nitrum_." [8] This paragraph displays hopeless ignorance. Borax was known to Agricola and greatly used in his time; it certainly was not made from these compounds, but was imported from Central Asia. Sal-ammoniac was also known in his time, and was used like borax as a soldering agent. The reaction given by Agricola would yield free ammonia. The following historical notes on borax and sal-ammoniac may be of service. BORAX.--The uncertainties of the ancient distinctions in salts involve borax deeply. The word _Baurach_ occurs in Geber and the other early Alchemistic writings, but there is nothing to prove that it was modern borax. There cannot be the slightest doubt, however, that the material referred to by Agricola as _borax_ was our borax, because of the characteristic qualities incidentally mentioned in Book VII. That he believed it was an artificial product from _nitrum_ is evident enough from his usual expression "_chrysocolla_ made from _nitrum_, which the Moors call _borax_." Agricola, in _De Natura Fossilium_ (p. 206-7), makes the following statements, which could leave no doubt on the subject:--"Native _nitrum_ is found in the earth or on the surface.... It is from this variety that the Venetians make _chrysocolla_, which I call _borax_.... The second variety of artificial _nitrum_ is made at the present day from the native _nitrum_, called by the Arabs _tincar_, but I call it usually by the Greek name _chrysocolla_; it is really the Arabic _borax_.... This _nitrum_ does not decrepitate nor fly out of the fire; however, the native variety swells up from within." The application of the word _chrysocolla_ (_chrysos_, gold; _colla_, solder) to soldering materials, and at the same time to the copper mineral, is of Greek origin. If any further proof were needed as to the substance meant by Agricola, it lies in the word _tincar_. For a long time the borax of Europe was imported from Central Asia, through Constantinople and Venice, under the name of _tincal_ or _tincar_. When this trade began, we do not know; evidently before Agricola's time. The statement here of making borax from alum and sal-ammoniac is identical with the assertion of Biringuccio (II., 9). SAL-AMMONIAC.--The early history of this--ammonium chloride--is also under a cloud. Pliny (XXXI., 39) speaks of a _sal-hammoniacum_, and Dioscorides (V., 85) uses much the same word. Pliny describes it as from near the temple of Ammon in Egypt. None of the distinctive characteristics of sal-ammoniac are mentioned, and there is every reason to believe it was either common salt or soda. Herodotus, Strabo, and others mention common salt sent from about the same locality. The first authentic mention is in Geber, who calls it _sal-ammoniacum_, and describes a method of making, and several characteristic reactions. It was known in the Middle Ages under various names, among them _sal-aremonicum_. Agricola (_De Nat. Fos._, III., p. 206) notes its characteristic quality of volatilization. "Sal-ammoniac ... in the fire neither crackles nor flies out, but is totally consumed." He also says (p. 208): "Borax is used by goldsmiths to solder gold, likewise silver. The artificers who make iron needles (tacks?) similarly use sal-ammoniac when they cover the heads with tin." The statement from Pliny mentioned in this paragraph is from XXXIII., 29, where he describes the _chrysocolla_ used as gold solder as made from verdigris, _nitrum_, and urine in the way quoted. It is quite possible that this solder was sal-ammoniac, though not made in quite this manner. Pliny refers in several places (XXXIII., 26, 27, 28, and 29, XXXV., 28, etc.) to _chrysocolla_, about which he is greatly confused as between gold-solder, the copper mineral, and a green pigment, the latter being of either mineral origin. [9] Saltpetre was secured in the Middle Ages in two ways, but mostly from the treatment of calcium nitrate efflorescence on cellar and similar walls, and from so-called saltpetre plantations. In this description of the latter, one of the most essential factors is omitted until the last sentence, _i.e._, that the nitrous earth was the result of the decay of organic or animal matter over a long period. Such decomposition, in the presence of potassium and calcium carbonates--the lye and lime--form potassium and calcium nitrates, together with some magnesium and sodium nitrates. After lixiviation, the addition of lye converts the calcium and magnesium nitrates into saltpetre, _i.e._, Ca(NO_{3})_{2} + K_{2}CO_{3} = CaCO_{3} + 2KNO_{3}. The carbonates precipitate out, leaving the saltpetre in solution, from which it was evaporated and crystallized out. The addition of alum as mentioned would scarcely improve the situation. The purification by repeated re-solution and addition of lye, and filtration, would eliminate the remaining other salts. The purification with sulphur, however, is more difficult to understand. In this case the saltpetre is melted and the sulphur added and set alight. Such an addition to saltpetre would no doubt burn brilliantly. The potassium sulphate formed would possibly settle to the bottom, and if the "greasy matter" were simply organic impurities, they might be burned off. This method of refining appears to have been copied from Biringuccio (X., 1), who states it in almost identical terms. HISTORICAL NOTE.--As mentioned in Note 6 above, it is quite possible that the Ancients did include efflorescence of walls under _nitrum_; but, so far as we are aware, no specific mention of such an occurrence of _nitrum_ is given, and, as stated before, there is every reason to believe that all the substances under that term were soda and potash. Especially the frequent mention of the preparation of _nitrum_ by way of burning, argues strongly against saltpetre being included, as they would hardly have failed to notice the decrepitation. Argument has been put forward that Greek fire contained saltpetre, but it amounts to nothing more than argument, for in those receipts preserved, no salt of any kind is mentioned. It is most likely that the leprosy of house-walls of the Mosaic code (Leviticus XIV., 34 to 53) was saltpetre efflorescence. The drastic treatment by way of destruction of such "unclean" walls and houses, however, is sufficient evidence that this salt was not used. The first certain mention of saltpetre (_sal petrae_) is in Geber. As stated before, the date of this work is uncertain; in any event it was probably as early as the 13th Century. He describes the making of "solvative water" with alum and saltpetre, so there can be no doubt as to the substance (see Note on p. 460, on nitric acid). There is also a work by a nebulous Marcus Graecus, where the word _sal petrosum_ is used. And it appears that Roger Bacon (died 1294) and Albertus Magnus (died 1280) both had access to that work. Bacon uses the term _sal petrae_ frequently enough, and was the first to describe gunpowder (_De Mirabili Potestate Artis et Naturae_ 1242). He gives no mention of the method of making his _sal petrae_. Agricola uses throughout the Latin text the term _halinitrum_, a word he appears to have coined himself. However, he gives its German equivalent in the _Interpretatio_ as _salpeter_. The only previous description of the method of making saltpetre, of which we are aware, is that of Biringuccio (1540), who mentions the boiling of the excrescences from walls, and also says a good deal about boiling solutions from "nitrous" earth, which may or may not be of "plantation" origin. He also gives this same method of refining with sulphur. In any event, this statement by Agricola is the first clear and complete description of the saltpetre "plantations." Saltpetre was in great demand in the Middle Ages for the manufacture of gunpowder, and the first record of that substance and of explosive weapons necessarily involves the knowledge of saltpetre. However, authentic mention of such weapons only begins early in the 14th Century. Among the earliest is an authority to the Council of Twelve at Florence to appoint persons to make cannon, etc., (1326), references to cannon in the stores of the Tower of London, 1388, &c. [10] There are three methods of manufacturing alum described by Agricola, the first and third apparently from shales, and the second from alum rock or "alunite." The reasons for assuming that the first process was from shales, are the reference to the "aluminous earth" as ore (_venae_) coming from "veins," and also the mixture of vitriol. In this process the free sulphuric acid formed by the oxidation of pyrites reacts upon the argillaceous material to form aluminium sulphate. The decomposed ore is then placed in tanks and lixiviated. The solution would contain aluminium sulphate, vitriol, and other impurities. By the addition of urine, the aluminium sulphate would be converted into ammonia alum. Agricola is, of course, mistaken as to the effect of the addition, being under the belief that it separated the vitriol from the alum; in fact, this belief was general until the latter part of the 18th Century, when Lavoisier determined that alum must have an alkali base. Nor is it clear from this description exactly how they were separated. In a condensed solution allowed to cool, the alum would precipitate out as "alum meal," and the vitriol would "float on top"--in solution. The reference to "meal" may represent this phenomenon, and the re-boiling referred to would be the normal method of purification by crystallization. The "asbestos" and gypsum deposited in the caldrons were no doubt feathery and mealy calcium sulphate. The alum produced would, in any event, be mostly ammonia alum. The second process is certainly the manufacture from "alum rock" or "alunite" (the hydrous sulphate of aluminium and potassium), such as that mined at La Tolfa in the Papal States, where the process has been for centuries identical with that here described. The alum there produced is the double basic potassium alum, and crystallizes into cubes instead of octahedra, _i.e._, the Roman alum of commerce. The presence of much ferric oxide gives the rose colour referred to by Agricola. This account is almost identical with that of Biringuccio (II., 4), and it appears from similarity of details that Agricola, as stated in his preface, must have "refreshed his mind" from this description; it would also appear from the preface that he had himself visited the locality. The third process is essentially the same as the first, except that the decomposition of the pyrites was hastened by roasting. The following obscure statement of some interest occurs in Agricola's _De Natura Fossilium_, p. 209:--"... alum is made from vitriol, for when oil is made from the latter, alum is distilled out (_expirat_). This absorbs the clay which is used in cementing glass, and when the operation is complete the clay is macerated with pure water, and the alum is soon afterward deposited in the shape of small cubes." Assuming the oil of vitriol to be sulphuric acid and the clay "used in cementing glass" to be kaolin, we have here the first suggestion of a method for producing alum which came into use long after. "Burnt alum" (_alumen coctum_).--Agricola frequently uses this expression, and on p. 568, describes the operation, and the substance is apparently the same as modern dehydrated alum, often referred to as "burnt alum." HISTORICAL NOTES.--Whether the Ancients knew of alum in the modern sense is a most vexed question. The Greeks refer to a certain substance as _stypteria_, and the Romans refer to this same substance as _alumen_. There can be no question as to their knowledge and common use of vitriol, nor that substances which they believed were entirely different from vitriol were comprised under the above names. Beckmann (Hist. of Inventions, Vol. I., p. 181) seems to have been the founder of the doctrine that the ancient _alumen_ was vitriol, and scores of authorities seem to have adopted his arguments without inquiry, until that belief is now general. One of the strongest reasons put forward was that alum does not occur native in appreciable quantities. Apart from the fact that the weight of this argument has been lost by the discovery that alum does occur in nature to some extent as an aftermath of volcanic action, and as an efflorescence from argillaceous rocks, we see no reason why the Ancients may not have prepared it artificially. One of the earliest mentions of such a substance is by Herodotus (II., 180) of a thousand talents of _stypteria_, sent by Amasis from Egypt as a contribution to the rebuilding of the temple of Delphi. Diodorus (V., 1) mentions the abundance which was secured from the Lipari Islands (Stromboli, etc.), and a small quantity from the Isle of Melos. Dioscorides (V., 82) mentions Egypt, Lipari Islands, Melos, Sardinia, Armenia, etc., "and generally in any other places where one finds red ochre (_rubrica_)." Pliny (XXXV., 52) gives these same localities, and is more explicit as to how it originates--"from an earthy water which exudes from the earth." Of these localities, the Lipari Islands (Stromboli, etc.), and Melos are volcanic enough, and both Lipari and Melos are now known to produce natural alum (Dana. Syst. Min., p. 95; and Tournefort, "_Relation d'un voyage du Levant_." London, 1717, _Lettre_ IV., Vol. 1.). Further, the hair-like alum of Dioscorides, repeated by Pliny below, was quite conceivably fibrous _kalinite_, native potash alum, which occurs commonly as an efflorescence. Be the question of native alum as it may--and vitriol is not much more common--our own view that the ancient _alumen_ was alum, is equally based upon the artificial product. Before entering upon the subject, we consider it desirable to set out the properties of the ancient substance, a complete review of which is given by Pliny (XXXV., 52), he obviously quoting also from Dioscorides, which, therefore, we do not need to reproduce. Pliny says:-- "Not less important, or indeed dissimilar, are the uses made of _alumen_; by which name is understood a sort of salty earth. Of this, there are several kinds. In Cyprus there is a white _alumen_, and a darker kind. There is not a great difference in their colour, though the uses made of them are very dissimilar,--the white _alumen_ being employed in a liquid state for dyeing wool bright colours, and the dark-coloured _alumen_, on the other hand, for giving wool a sombre tint. Gold is purified with black _alumen_. Every kind of _alumen_ is from a _limus_ water which exudes from the earth. The collection of it commences in winter, and it is dried by the summer sun. That portion of it which first matures is the whitest. It is obtained in Spain, Egypt, Armenia, Macedonia, Pontus, Africa, and the islands of Sardinia, Melos, Lipari, and Strongyle; the most esteemed, however, is that of Egypt, the next best from Melos. Of this last there are two kinds, the liquid _alumen_, and the solid. Liquid _alumen_, to be good, should be of a limpid and milky appearance; when rubbed, it should be without roughness, and should give a little heat. This is called _phorimon_. The mode of detecting whether it has been adulterated is by pomegranate juice, for, if genuine, the mixture turns black. The other, or solid, is pale and rough and turns dark with nut-galls; for which reason it is called _paraphoron_. Liquid _alumen_ is naturally astringent, indurative, and corrosive; used in combination with honey, it heals ulcerations.... There is one kind of solid _alumen_, called by the Greeks _schistos_, which splits into filaments of a whitish colour; for which reason some prefer calling it _trichitis_ (hair like). _Alumen_ is produced from the stone _chalcitis_, from which copper is also made, being a sort of coagulated scum from that stone. This kind of _alumen_ is less astringent than the others, and is less useful as a check upon bad humours of the body.... The mode of preparing it is to cook it in a pan until it has ceased being a liquid. There is another variety of _alumen_ also, of a less active nature, called _strongyle_. It is of two kinds. The fungous, which easily dissolves, is utterly condemned. The better kind is the pumice-like kind, full of small holes like a sponge, and is in round pieces, more nearly white in colour, somewhat greasy, free from grit, friable, and does not stain black. This last kind is cooked by itself upon charcoal until it is reduced to pure ashes. The best kind of all is that called _melinum_, from the Isle of Melos, as I have said, none being more effectual as an astringent, for staining black, and for indurating, and none becomes more dry.... Above all other properties of _alumen_ is its remarkable astringency, whence its Greek name.... It is injected for dysentry and employed as a gargle." The lines omitted refer entirely to medical matters which have no bearing here. The following paragraph (often overlooked) from Pliny (XXXV., 42) also has an important bearing upon the subject:--"In Egypt they employ a wonderful method of dyeing. The white cloth, after it is pressed, is stained in various places, not with dye stuffs, but with substances which absorb colours. These applications are not apparent on the cloth, but when it is immersed in a caldron of hot dye it is removed the next moment brightly coloured. The remarkable circumstance is that although there be only one dye in the caldron yet different colours appear in the cloth." It is obvious from Pliny's description above, and also from the making of vitriol (see Note 11, p. 572), that this substance was obtained from liquor resulting from natural or artificial lixiviation of rocks--in the case of vitriols undoubtedly the result of decomposition of pyritiferous rocks (such as _chalcitis_). Such liquors are bound to contain aluminum sulphate if there is any earth or clay about, and whether they contained alum would be a question of an alkali being present. If no alkali were present in this liquor, vitriol would crystallize out first, and subsequent condensation would yield aluminum sulphate. If alkali were present, the alum would crystallize out either before or with the vitriol. Pliny's remark, "that portion of it which first matures is whitest", agrees well enough with this hypothesis. No one will doubt that some of the properties mentioned above belong peculiarly to vitriol, but equally convincing are properties and uses that belong to alum alone. The strongly astringent taste, white colour, and injection for dysentry, are more peculiar to alum than to vitriol. But above all other properties is that displayed in dyeing, for certainly if we read this last quotation from Pliny in conjunction with the statement that white _alumen_ produces bright colours and the dark kind, sombre colours, we have the exact reactions of alum and vitriol when used as mordants. Therefore, our view is that the ancient salt of this character was a more or less impure mixture ranging from alum to vitriol--"the whiter the better." Further, considering the ancient knowledge of soda (_nitrum_), and the habit of mixing it into almost everything, it does not require much flight of imagination to conceive its admixture to the "water," and the absolute production of alum. Whatever may have been the confusion between alum and vitriol among the Ancients, it appears that by the time of the works attributed to Geber (12th or 13th Century), the difference was well known. His work (_Investigationes perfectiones_, IV.) refers to _alumen glaciale_ and _alumen jameni_ as distinguished from vitriol, and gives characteristic reactions which can leave no doubt as to the distinction. We may remark here that the repeated statement apparently arising from Meyer (History of Chemistry, p. 51) that Geber used the term _alum de rocca_ is untrue, this term not appearing in the early Latin translations. During the 15th Century alum did come to be known in Europe as _alum de rocca_. Various attempts have been made to explain the origin of this term, ranging from the Italian root, a "rock," to the town of Rocca in Syria, where alum was supposed to have been produced. In any event, the supply for a long period prior to the middle of the 15th Century came from Turkey, and the origin of the methods of manufacture described by Agricola, and used down to the present day, must have come from the Orient. In the early part of the 15th Century, a large trade in alum was done between Italy and Asia Minor, and eventually various Italians established themselves near Constantinople and Smyrna for its manufacture (Dudae, _Historia Byzantina Venetia_, 1729, p. 71). The alum was secured by burning the rock, and lixiviation. With the capture of Constantinople by the Turks (1453), great feeling grew up in Italy over the necessity of buying this requisite for their dyeing establishments from the infidel, and considerable exertion was made to find other sources of supply. Some minor works were attempted, but nothing much eventuated until the appearance of one John de Castro. From the Commentaries of Pope Pius II. (1614, p. 185), it appears that this Italian had been engaged in dyeing cloth in Constantinople, and thus became aware of the methods of making alum. Driven out of that city through its capture by the Turks, he returned to Italy and obtained an office under the Apostolic Chamber. While in this occupation he discovered a rock at Tolfa which appeared to him identical with that used at Constantinople in alum manufacture. After experimental work, he sought the aid of the Pope, which he obtained after much vicissitude. Experts were sent, who after examination "shed tears of joy, they kneeling down three times, worshipped God and praised His kindness in conferring such a gift on their age." Castro was rewarded, and the great papal monopoly was gradually built upon this discovery. The industry firmly established at Tolfa exists to the present day, and is the source of the Roman alum of commerce. The Pope maintained this monopoly strenuously, by fair means and by excommunication, gradually advancing the price until the consumers had greater complaint than against the Turks. The history of the disputes arising over the papal alum monopoly would alone fill a volume. By the middle of the 15th Century alum was being made in Spain, Holland, and Germany, and later in England. In her efforts to encourage home industries and escape the tribute to the Pope, Elizabeth (see Note on p. 283) invited over "certain foreign chymistes and mineral masters" and gave them special grants to induce them to "settle in these realmes." Among them was Cornelius Devoz, to whom was granted the privilege of "mining and digging in our Realm of England for allom and copperas." What Devoz accomplished is not recorded, but the first alum manufacture on a considerable scale seems to have been in Yorkshire, by one Thomas Chaloner (about 1608), who was supposed to have seduced workmen from the Pope's alum works at Tolfa, for which he was duly cursed with all the weight of the Pope and Church. (Pennant, Tour of Scotland, 1786). [11] The term for vitriol used by the Roman authors, followed by Agricola, is _atramentum sutorium_, literally shoemaker's blacking, the term no doubt arising from its ancient (and modern) use for blackening leather. The Greek term was _chalcanthon_. The term "vitriol" seems first to appear in Albertus Magnus (_De Mineralibus_, _Liber_ V.), who died in 1280, where he uses the expression "_atramentum viride a quibusdam vitreolum vocatur_." Agricola (_De Nat. Foss._, p. 213) states, "In recent years the name _vitriolum_ has been given to it." The first adequate description of vitriol is by Dioscorides (V., 76), as follows:--"Vitriol (_chalcanthon_) is of one genus, and is a solidified liquid, but it has three different species. One is formed from the liquids which trickle down drop by drop and congeal in certain mines; therefore those who work in the Cyprian mines call it _stalactis_. Petesius calls this kind _pinarion_. The second kind is that which collects in certain caverns; afterward it is poured into trenches, where it congeals, whence it derives its name _pectos_. The third kind is called _hephthon_ and is mostly made in Spain; it has a beautiful colour but is weak. The manner of preparing it is as follows: dissolving it in water, they boil it, and then they transfer it to cisterns and leave it to settle. After a certain number of days it congeals and separates into many small pieces, having the form of dice, which stick together like grapes. The most valued is blue, heavy, dense, and translucent." Pliny (XXXIV., 32) says:--"By the name which they have given to it, the Greeks indicate the similar nature of copper and _atramentum sutorium_, for they call it _chalcanthon_. There is no substance of an equally miraculous nature. It is made in Spain from wells of this kind of water. This water is boiled with an equal quantity of pure water, and is then poured into wooden tanks (fish ponds). Across these tanks there are fixed beams, to which hang cords stretched by little stones. Upon these cords adheres the _limus_ (Agricola's 'juice') in drops of a vitreous appearance, somewhat resembling a bunch of grapes. After removal, it is dried for thirty days. It is of a blue colour, and of a brilliant lustre, and is very like glass. Its solution is the blacking used for colouring leather. _Chalcanthon_ is made in many other ways: its kind of earth is sometimes dug from ditches, from the sides of which exude drops, which solidify by the winter frosts into icicles, called _stalagmia_, and there is none more pure. When its colour is nearly white, with a slight tinge of violet, it is called _leukoion_. It is also made in rock basins, the rain water collecting the _limus_ into them, where it becomes hardened. It is also made in the same way as salt by the intense heat of the sun. Hence it is that some distinguish two kinds, the mineral and the artificial; the latter being paler than the former and as much inferior to it in quality as it is in colour." While Pliny gives prominence to blue vitriol, his solution for colouring leather must have been the iron sulphate. There can be no doubt from the above, however, that both iron and copper sulphates were known to the Ancients. From the methods for making vitriol given here in _De Re Metallica_, it is evident that only the iron sulphate would be produced, for the introduction of iron strips into the vats would effectually precipitate any copper. It is our belief that generally throughout this work, the iron sulphate is meant by the term _atramentum sutorium_. In _De Natura Fossilium_ (p. 213-15) Agricola gives three varieties of _atramentum sutorium_,--_viride_, _caeruleum_, and _candidum_, _i.e._, green, blue, and white. Thus the first mention of white vitriol (zinc sulphate) appears to be due to him, and he states further (p. 213): "A white sort is found, especially at Goslar, in the shape of icicles, transparent like crystals." And on p. 215: "Since I have explained the nature of vitriol and its relatives, which are obtained from cupriferous pyrites, I will next speak of an acrid solidified juice which commonly comes from _cadmia_. It is found at Annaberg in the tunnel driven to the Saint Otto mine; it is hard and white, and so acrid that it kills mice, crickets, and every kind of animal. However, that feathery substance which oozes out from the mountain rocks and the thick substance found hanging in tunnels and caves from which saltpetre is made, while frequently acrid, does not come from _cadmia_." Dana (Syst. of Min., p. 939) identifies this as _Goslarite_--native zinc sulphate. It does not appear, however, that artificial zinc vitriol was made in Agricola's time. Schlueter (_Huette-Werken_, Braunschweig 1738, p. 597) states it to have been made for the first time at Rammelsberg about 1570. It is desirable here to enquire into the nature of the substances given by all of the old mineralogists under the Latinized Greek terms _chalcitis_, _misy_, _sory_, and _melanteria_. The first mention of these minerals is in Dioscorides, who (V., 75-77) says: "The best _chalcitis_ is like copper. It is friable, not stony, and is intersected by long brilliant veins.... _Misy_ is obtained from Cyprus; it should have the appearance of gold, be hard, and when pulverised it should have the colour of gold and sparkle like stars. It has the same properties as _chalcitis_.... The best is from Egypt.... One kind of _melanteria_ congeals like salt in the entries to copper mines. The other kind is earthy and appears on the surface of the aforesaid mines. It is found in the mines of Cilicia and other regions. The best has the colour of sulphur, is smooth, pure, homogenous, and upon contact with water immediately becomes black.... Those who consider _sory_ to be the same as _melanteria_, err greatly. _Sory_ is a species of its own, though it is not dissimilar. The smell of _sory_ is oppressive and provokes nausea. It is found in Egypt and in other regions, as Libya, Spain, and Cyprus. The best is from Egypt, and when broken is black, porous, greasy, and astringent." Pliny (XXXIV., 29-31) says:--"That is called _chalcitis_ from which, as well as itself copper (?) is extracted by heat. It differs from _cadmia_ in that this is obtained from rocks near the surface, while that is taken from rocks below the surface. Also _chalcitis_ is immediately friable, being naturally so soft as to appear like compressed wool. There is also this other distinction; _chalcitis_ contains three other substances, copper, _misy_, and _sory_. Of each of these we shall speak in their appropriate places. It contains elongated copper veins. The most approved kind is of the colour of honey; it is streaked with fine sinuous veins and is friable and not stony. It is considered most valuable when fresh.... The _sory_ of Egypt is the most esteemed, being much superior to that of Cyprus, Spain, and Africa; although some prefer the _sory_ from Cyprus for affections of the eyes. But from whatever nation it comes, the best is that which has the strongest odour, and which, when ground up, becomes greasy, black, and spongy. It is a substance so unpleasant to the stomach that some persons are nauseated by its smell. Some say that _misy_ is made by the burning of stones in trenches, its fine yellow powder being mixed with the ashes of pine-wood. The truth is, as I said above, that though obtained from the stone, it is already made and in solid masses, which require force to detach them. The best comes from the works of Cyprus, its characteristics being that when broken it sparkles like gold, and when ground it presents a sandy appearance, but on the contrary, if heated, it is similar to _chalcitis_. _Misy_ is used in refining gold...." Agricola's views on the subject appear in _De Natura Fossilium_. He says (p. 212):--"The cupriferous pyrites (_pyrites aerosus_) called _chalcitis_ is the mother and cause of _sory_--which is likewise known as mine _vitriol_ (_atramentum metallicum_)--and _melanteria_. These in turn yield vitriol and such related things. This may be seen especially at Goslar, where the nodular lumps of dark grey colour are called vitriol stone (_lapis atramenti_). In the centre of them is found greyish pyrites, almost dissolved, the size of a walnut. It is enclosed on all sides, sometimes by _sory_, sometimes by _melanteria_. From them start little veinlets of greenish vitriol which spread all over it, presenting somewhat the appearance of hairs extending in all directions and cohering together.... There are five species of this solidified juice, _melanteria_, _sory_, _chalcitis_, _misy_, and vitriol. Sometimes many are found in one place, sometimes all of them, for one originates from the other. From pyrites, which is, as one might say, the root of all these juices, originates the above-mentioned _sory_ and _melanteria_. From _sory_, _chalcitis_, and _melanteria_ originate the various kinds of vitriol.... _Sory_, _melanteria_, _chalcitis_, and _misy_ are always native; vitriol alone is either native or artificial. From them vitriol effloresces white, and sometimes green or blue. _Misy_ effloresces not only from _sory_, _melanteria_, and _chalcitis_, but also from all the vitriols, artificial as well as natural.... _Sory_ and _melanteria_ differ somewhat from the others, but they are of the same colours, grey and black; but _chalcitis_ is red and copper-coloured; _misy_ is yellow or gold-coloured. All these native varieties have the odour of lightning (brimstone), but _sory_ is the most powerful. The feathery vitriol is soft and fine and hair-like, and _melanteria_ has the appearance of wool and it has a similarity to salt; all these are rare and light; _sory_, _chalcitis_, and _misy_ have the following relations. _Sory_ because of its density has the hardness of stone, although its texture is very coarse. _Misy_ has a very fine texture. _Chalcitis_ is between the two; because of its roughness and strong odour it differs from _melanteria_, although they do not differ in colour. The vitriols, whether natural or artificial, are hard and dense ... as regarding shape, _sory_, _chalcitis_, _misy_, and _melanteria_ are nodular, but _sory_ is occasionally porous, which is peculiar to it. _Misy_ when it effloresces in no great quantity from the others is like a kind of pollen, otherwise it is nodular. _Melanteria_ sometimes resembles wool, sometimes salt." The sum and substance, therefore, appears to be that _misy_ is a yellowish material, possibly ochre, and _sory_ a blackish stone, both impregnated with vitriol. _Chalcitis_ is a partially decomposed pyrites; and _melanteria_ is no doubt native vitriol. From this last term comes the modern _melanterite_, native hydrous ferrous sulphate. Dana (System of Mineralogy, p. 964) considers _misy_ to be in part _copiapite_--basic ferric sulphate--but any such part would not come under Agricola's objection to it as a source of vitriol. The disabilities of this and _chalcitis_ may, however, be due to their copper content. [12] Agricola (_De Nat. Fos._, 221) says:--"There is a species of artificial sulphur made from sulphur and iron hammer-scales, melted together and poured into moulds. This, because it heals scabs of horses, is generally called _caballinum_." It is difficult to believe such a combination was other than iron sulphide, but it is equally difficult to understand how it was serviceable for this purpose. [13] Inasmuch as pyrites is discussed in the next paragraph, the material of the first distillation appears to be native sulphur. Until the receiving pots became heated above the melting point of the sulphur, the product would be "flowers of sulphur," and not the wax-like product. The equipment described for pyrites in the next paragraph would be obviously useful only for coarse material. But little can be said on the history of sulphur; it is mentioned often enough in the Bible and also by Homer (Od. XXII., 481). The Greeks apparently knew how to refine it, although neither Dioscorides nor Pliny specifically describes such an operation. Agricola says (_De Nat. Fos._, 220): "Sulphur is of two kinds; the mineral, which the Latins call _vivum_, and the Greeks _apyron_, which means 'not exposed to the fire' (_ignem non expertum_) as rightly interpreted by Celsius; and the artificial, called by the Greeks _pepyromenon_, that is, 'exposed to the fire.'" In Book X., the expression _sulfur ignem non expertum_ frequently appears, no doubt in Agricola's mind for native sulphur, although it is quite possible that the Greek distinction was between "flowers" of sulphur and the "wax-like" variety. [14] The substances referred to under the names _bitumen_, _asphalt_, _maltha_, _naphtha_, _petroleum_, _rock-oil_, etc., have been known and used from most ancient times, and much of our modern nomenclature is of actual Greek and Roman ancestry. These peoples distinguished three related substances,--the Greek _asphaltos_ and Roman _bitumen_ for the hard material,--Greek _pissasphaltos_ and Roman _maltha_ for the viscous, pitchy variety--and occasionally the Greek _naphtha_ and Roman _naphtha_ for petroleum proper, although it is often enough referred to as liquid _bitumen_ or liquid _asphaltos_. The term _petroleum_ apparently first appears in Agricola's _De Natura Fossilium_ (p. 222), where he says the "oil of bitumen ... now called _petroleum_." Bitumen was used by the Egyptians for embalming from pre-historic times, _i.e._, prior to 5000 B.C., the term "mummy" arising from the Persian word for bitumen, _mumiai_. It is mentioned in the tribute from Babylonia to Thotmes III., who lived about 1500 B.C. (Wilkinson, Ancient Egyptians I., p. 397). The Egyptians, however, did not need to go further afield than the Sinai Peninsula for abundant supplies. Bitumen is often cited as the real meaning of the "slime" mentioned in Genesis (XI., 3; XIV., 10), and used in building the Tower of Babel. There is no particular reason for this assumption, except the general association of Babel, Babylon, and Bitumen. However, the Hebrew word _sift_ for pitch or bitumen does occur as the cement used for Moses's bulrush cradle (Exodus II., 3), and Moses is generally accounted about 1300 B.C. Other attempts to connect Biblical reference to petroleum and bitumen revolve around Job XXIX., 6, Deut. XXXII., 13, Maccabees II., I, 18, Matthew V., 13, but all require an unnecessary strain on the imagination. The plentiful occurrence of bitumen throughout Asia Minor, and particularly in the Valley of the Euphrates and in Persia, is the subject of innumerable references by writers from Herodotus (484-424 B.C.) down to the author of the company prospectus of recent months. Herodotus (I., 179) and Diodorus Siculus (I) state that the walls of Babylon were mortared with bitumen--a fact partially corroborated by modern investigation. The following statement by Herodotus (VI., 119) is probably the source from which Pliny drew the information which Agricola quotes above. In referring to a well at Ardericca, a place about 40 miles from ancient Susa, in Persia, Herodotus says:--"For from the well they get bitumen, salt, and oil, procuring it in the way that I will now describe: they draw with a swipe, and instead of a bucket they make use of the half of a wine-skin; with this the man dips and, after drawing, pours the liquid into a reservoir, wherefrom it passes into another, and there takes three different shapes. The salt and bitumen forthwith collect and harden, while the oil is drawn off into casks. It is called by the Persians _rhadinace_, is black, and has an unpleasant smell." (Rawlinson's Trans. III., p. 409). The statement from Pliny (XXXI., 39) here referred to by Agricola, reads:--"It (salt) is made from water of wells poured into salt-pans. At Babylon the first condensed is a bituminous liquid like oil which is burned in lamps. When this is taken off, salt is found beneath. In Cappadocia also the water from both wells and springs is poured into salt-pans." When petroleum began to be used as an illuminant it is impossible to say. A passage in Aristotle's _De Mirabilibus_ (127) is often quoted, but in reality it refers only to a burning spring, a phenomenon noted by many writers, but from which to its practical use is not a great step. The first really definite statement as to the use of petroleum as an illuminant is Strabo's quotation (XVI., 1, 15) from Posidonius: "Asphaltus is found in great abundance in Babylonia. Eratosthenes describes it as follows:--The liquid _asphaltus_, which is called _naphtha_, is found in Susa; the dry kind, which can be made solid, in Babylonia. There is a spring of it near the Euphrates.... Others say that the liquid kind is also found in Babylonia.... The liquid kind, called _naphtha_, is of a singular nature. When it is brought near the fire, the fire catches it.... Posidonius says that there are springs of _naphtha_ in Babylonia, some of which produce white, others black _naphtha_; the first of these, I mean white _naphtha_, which attracts flame, is liquid sulphur; the second or black _naphtha_ is liquid _asphaltus_, and is burnt in lamps instead of oil." (Hamilton's Translation, Vol. III., p. 151). Eratosthenes lived about 200 B.C., and Posidonius about 100 years later. Dioscorides (I., 83), after discussing the usual sources of bitumen says: "It is found in a liquid state in Agrigentum in Sicily, flowing on streams; they use it for lights in lanterns in place of oil. Those who call the Sicilian kind oil are under a delusion, for it is agreed that it is a kind of liquid bitumen." Pliny adds nothing much new to the above quotations, except in regard to these same springs (XXXV., 51) that "The inhabitants collect it on the panicles of reeds, to which it quickly adheres and they use it for burning in lamps instead of oil." Agricola (_De Natura Fossilium_, Book IV.) classifies petroleum, coal, jet, and obsidian, camphor, and amber as varieties of bitumen, and devotes much space to the refutation of the claims that the last two are of vegetable origin. [15] Agricola (_De Natura Fossilium_, p. 215) in discussing substances which originate from copper, gives among them green _chrysocolla_ (as distinguished from borax, etc., see Note 8 above), and says: "Native _chrysocolla_ originates in veins and veinlets, and is found mostly by itself like sand, or adhering to metallic substances, and when scraped off from this appears similar to its own sand. Occasionally it is so thin that very little can be scraped off. Or else it occurs in waters which, as I have said, wash these minerals, and afterward it settles as a powder. At Neusohl in the Carpathians, green water flowing from an ancient tunnel wears away this _chrysocolla_ with it. The water is collected in thirty large reservoirs, where it deposits the _chrysocolla_ as a sediment, which they collect every year and sell,"--as a pigment. This description of its occurrence would apply equally well to modern _chrysocolla_ or to malachite. The solution from copper ores would deposit some sort of green incrustation, of carbonates mostly. [16] The statement in Pliny (XXXVI., 66) to which Agricola refers is as follows: "Then as ingenuity was not content with the mixing of _nitrum_, they began the addition of _lapis magnes_, because of the belief that it attracts liquefied glass as well as iron. In a similar manner many kinds of brilliant stones began to be added to the melting, and then shells and fossil sand. Authors tell us that the glass of India is made of broken crystal, and in consequence nothing can compare with it. Light and dry wood is used for fusing, _cyprium_ (copper?) and _nitrum_ being added, particularly _nitrum_ from Ophir etc." A great deal of discussion has arisen over this passage, in connection with what this _lapis magnes_ really was. Pliny (XXXVI., 25) describes the lodestone under this term, but also says: "There (in Ethiopia) also is _haematites magnes_, a stone of blood colour, which shows a red colour if crushed, or of saffron. The _haematites_ has not the same property of attracting iron as _magnes_." Relying upon this sentence for an exception to the ordinary sort of _magnes_, and upon the impossible chemical reaction involved, most commentators have endeavoured to show that lodestone was not the substance meant by Pliny, but manganese, and thus they find here the first knowledge of this mineral. There can be little doubt that Pliny assumed it to be the lodestone, and Agricola also. Whether the latter had any independent knowledge on this point in glass-making or was merely quoting Pliny--which seems probable--we do not know. In any event, Biringuccio, whose work preceded _De Re Metallica_ by fifteen years, does definitely mention manganese in this connection. He dismisses this statement of Pliny with the remark (p. 37-38): "The Ancients wrote about lodestones, as Pliny states, and they mixed it together with _nitrum_ in their first efforts to make glass." The following passage from this author (p. 36-37), however, is not only of interest in this connection, but also as possibly being the first specific mention of manganese under its own name. Moreover, it has been generally overlooked in the many discussions of the subject. "Of a similar nature (to _zaffir_) is also another mineral called _manganese_, which is found, besides in Germany, at the mountain of Viterbo in Tuscany ... it is the colour of _ferrigno scuro_ (iron slag?). In melting it one cannot obtain any metal ... but it gives a very fine colour to glass, so that the glass workers use it in their pigments to secure an azure colour.... It also has such a property that when put into melted glass it cleanses it and makes it white, even if it were green or yellow. In a hot fire it goes off in a vapour like lead, and turns into ashes." To enter competently into the discussion of the early history of glass-making would employ more space than can be given, and would lead but to a sterile end. It is certain that the art was pre-Grecian, and that the Egyptians were possessed of some knowledge of making and blowing it in the XI Dynasty (according to Petrie 3,500 B.C.), the wall painting at Beni Hassen, which represents glass-blowing, being attributed to that period. The remains of a glass factory at Tel el Amarna are believed to be of the XVIII Dynasty. (Petrie, 1,500 B.C.). The art reached a very high state of development among the Greeks and Romans. No discussion of this subject omits Pliny's well-known story (XXXVI, 65), which we also add: "The tradition is that a merchant ship laden with _nitrum_ being moored at this place, the merchants were preparing their meal on the beach, and not having stones to prop up their pots, they used lumps of _nitrum_ from the ship, which fused and mixed with the sands of the shore, and there flowed streams of a new translucent liquid, and thus was the origin of glass." APPENDIX A. AGRICOLA'S WORKS. Georgius Agricola was not only the author of works on Mining and allied subjects, usually associated with his name, but he also interested himself to some extent in political and religious subjects. For convenience in discussion we may, therefore, divide his writings on the broad lines of (1) works on mining, geology, mineralogy, and allied subjects; (2) works on other subjects, medical, religious, critical, political, and historical. In respect especially to the first division, and partially with regard to the others, we find three principal cases: (_a_) Works which can be authenticated in European libraries to-day; (_b_) references to editions of these in bibliographies, catalogues, etc., which we have been unable to authenticate; and (_c_) references to works either unpublished or lost. The following are the short titles of all of the published works which we have been able to find on the subjects allied to mining, arranged according to their present importance:--_De Re Metallica_, first edition, 1556; _De Natura Fossilium_, first edition, 1546; _De Ortu et Causis Subterraneorum_, first edition, 1546; _Bermannus_, first edition, 1530; _Rerum Metallicarum Interpretatio_, first edition, 1546; _De Mensuris et Ponderibus_, first edition, 1533; _De Precio Metallorum et Monetis_, first edition, 1550; _De Veteribus et Novis Metallis_, first edition, 1546; _De Natura eorum quae Effluunt ex Terra_, first edition, 1546; _De Animantibus Subterraneis_, first edition, 1549. Of the "lost" or unpublished works, on which there is some evidence, the following are the most important:--_De Metallicis et Machinis_, _De Ortu Metallorum Defensio ad Jacobum Scheckium_, _De Jure et Legibus Metallicis_, _De Varia Temperie sive Constitutione Aeris_, _De Terrae Motu_, and _Commentariorum, Libri VI_. The known published works upon other subjects are as follows:--Latin Grammar, first edition, 1520; Two Religious Tracts, first edition, 1522; _Galen_ (Joint Revision of Greek Text), first edition, 1525; _De Bello adversus Turcam_, first edition, 1528; _De Peste_, first edition, 1554. The lost or partially completed works on subjects unrelated to mining, of which some trace has been found, are:--_De Medicatis Fontibus_, _De Putredine solidas partes_, etc., _Castigationes in Hippocratem_, _Typographia Mysnae et Toringiae_, _De Traditionibus Apostolicis_, _Oratio de rebus gestis Ernesti et Alberti_, _Ducum Saxoniae_. REVIEW OF PRINCIPAL WORKS. Before proceeding with the bibliographical detail, we consider it desirable to review briefly the most important of the author's works on subjects related to mining. _De Natura Fossilium._ This is the most important work of Agricola, excepting _De Re Metallica_. It has always been printed in combination with other works, and first appeared at Basel, 1546. This edition was considerably revised by the author, the amended edition being that of 1558, which we have used in giving references. The work comprises ten "books" of a total of 217 folio pages. It is the first attempt at systematic mineralogy, the minerals[1] being classified into (1) "earths" (clay, ochre, etc.), (2) "stones properly so-called" (gems, semi-precious and unusual stones, as distinguished from rocks), (3) "solidified juices" (salt, vitriol, alum, etc.), (4) metals, and (5) "compounds" (homogeneous "mixtures" of simple substances, thus forming such minerals as galena, pyrite, etc.). In this classification Agricola endeavoured to find some fundamental basis, and therefore adopted solubility, fusibility, odour, taste, etc., but any true classification without the atomic theory was, of course, impossible. However, he makes a very creditable performance out of their properties and obvious characteristics. All of the external characteristics which we use to-day in discrimination, such as colour, hardness, lustre, etc., are enumerated, the origin of these being attributed to the proportions of the Peripatetic elements and their binary properties. Dana, in his great work[2], among some fourscore minerals which he identifies as having been described by Agricola and his predecessors, accredits a score to Agricola himself. It is our belief, however, that although in a few cases Agricola has been wrongly credited, there are still more of which priority in description might be assigned to him. While a greater number than fourscore of so-called species are given by Agricola and his predecessors, many of these are, in our modern system, but varieties; for instance, some eight or ten of the ancient species consist of one form or another of silica.