300. Both these authors refer to Fuller’s British Worthies. [The carp

existed in England before the year 1486: for in Dame Juliana Berners’ work on Angling, which was published at St. Albans (hence called the Book of St. Albans) in 1486, we find the following passage: speaking of the carp, she says “That it is a deyntous fysshe, but there ben but few in Englonde. And therefore I wryte the lesse of hym. He is an euyll fysshe to take. For he is so stronge enarmyd in the mouthe, that there maye noo weke harnays hold him.”] CAMP-MILLS. Under this appellation are understood portable or moveable mills, which can be used, particularly in the time of war, when there are neither wind- nor water-mills in the neighbourhood, and which on that account formerly accompanied armies in the same manner as camp-ovens and camp-forges. Some of these mills have stones for grinding the corn, and others are constructed with a notched roller like those of our coffee-mills. Some of them also are so contrived that the machinery is put in motion by the revolution of the wheels of the carriage on which they are placed; and others, and perhaps the greater part of those used, are driven by horses or men, after the wheels of the carriage are sunk in the ground, or fastened in some other manner. To the latter kind belongs that mill of which Zonca[129] has given a coarse engraving, but without any description. He says it was invented by Pompeo Targone, engineer to the well-known marquis Ambrose Spinola; and he seems to place the time of the invention about the end of the sixteenth century. This mill is the same as that described by Beyer in his Theatrum Machinarum Molarium, and represented in the twenty-seventh plate of that work[130]. Beyer remarks that it was employed by Spinola. The inventor, as his name shows, was an Italian, who made himself known, in particular, at the celebrated siege of Rochelle, under Louis XIII., at which he was chosen to assist, because in the year 1603, when with Spinola, who was consulted respecting the operations at Rochelle, he had helped by means of a mole to shut the harbour of Ostend during the tedious siege of that place. He was likewise in the French service, as _intendant des machines du roi_; but his numerous and expensive undertakings did not succeed according to his expectations[131]. He invented also a particular kind of gun-carriages, and a variety of warlike machines[132]. Another old figure of such a mill was shown to me by Professor Meister, in Recueil de Plusieurs Machines Militaires, printed in 1620. This machine was driven by the wheels of the carriage; but whether it was ever used the author does not inform us. Lancellotti[133] ascribes this invention to the Germans, about the year 1633. Carriages for transporting camp-forges and mill-machinery are mentioned by Leonard Fronsperger[134], but he does not say whether complete mills were affixed to them. FOOTNOTES [129] Novo Teatro di Machine ed Edificii, di Vittorio Zonca. Padoua, 1621, and reprinted in 1656, fol. The greater part of the machines delineated in this scarce book are engines for raising heavy bodies; but many of them are used in various trades and manufactures, and may serve in some measure to illustrate the history of them. [130] J. M. Beyer’s Schauplatz der Mühlen-Bau-kunst. Leipzig, 1735, fol. Reprinted at Dresden, 1767. [131] All those authors who have written expressly on the fate of the Huguenots, the History of Richelieu, Louis XIII., and the siege of Rochelle, make mention of Targone. [132] Histoire de la Milice Françoise, par Daniel. Amst. 1724, i. p. 332. [133] L’Hoggidi, overo gl’Ingegni non inferiori a’ passati. Ven. 1636, 8vo. [134] Kriegsbuch, Frankf. 1596, fol. p. 9. MIRRORS[135]. It is highly probable that a limpid brook was the first mirror[136], but we have reason to think that artificial mirrors were made as mankind began to exercise their art and ingenuity on metals and stones. Every solid body, capable of receiving a fine polish, would be sufficient for this purpose; and indeed the oldest mirrors mentioned in history were of metal. Those which occur in Job[137] are praised on account of their hardness and solidity; and Moses relates[138], that the brazen laver, or washing-basin, was made from the mirrors of the women who had assembled at the door of the tabernacle to present them, and which he caused them to deliver up. As the women appeared in full dress at divine worship, it was necessary for them to have looking-glasses after the Egyptian manner. With these the washing-basins, according to the conjecture of most interpretators, were only ornamented, covered, or perhaps hung round; and Michaelis[139] himself was once of this opinion. But why should we not rather believe that the mirrors were melted and formed into washing-basins? As soon as mankind began to endeavour to make good mirrors of metal, they must have remarked that every kind of metal was not equally proper for that use, and that the best could be obtained only from a mixture of different metals. In the mirrors however which were collected by Moses, the artists had a sufficient stock of speculum metal, and were not under the necessity of making it themselves; and for this reason they could much more easily give to the whole basin a polished surface, in which the priests, when they washed, might survey themselves at full length. At any rate such a basin would not be the only one employed instead of a mirror. Artemidorus[140] says that he who dreams of viewing himself in a basin, will have a son born to him by his maid. Dreams indeed are generally as groundless as this interpretation; but one can hardly conjecture that Artemidorus would have thought of such a dream, had it not been very common for people to contemplate themselves in a basin. There were formerly a kind of fortune-tellers, who pretended to show in polished basins to the simple and ignorant, what they wished to know[141]. The ancients also had drinking-vessels, the inside of which was cut into mirrors, so disposed that the image of the person who drank from them was seen multiplied[142]. Vopiscus mentions, among the valuable presents of Valerian to the emperor Probus, when a tribune, a silver cup of great weight, which was covered on the inside with mirrors of this sort[143]. Menard and others conjecture that mirrors in the time of Homer were not much used, because he mentions them on no occasion, not even where he describes in so circumstantial a manner the toilet of Juno[144]. In answer to this, however, I have two things to observe. In the first place, it is not to be expected that Homer should have mentioned every article with which he was acquainted; and secondly, we are assured by Callimachus, where he evidently has imitated the passage of Homer before-quoted[145], that neither Juno nor Pallas employed a mirror when they dressed. Mythology therefore did not allow the poet to introduce a mirror upon the toilet of that deity. Polydore Vergilius, Boccace, Menard, and others have all fallen into the error of making Æsculapius the inventor of mirrors, though Cicero[146] seems to say the same thing; but the best commentators have long since observed very justly, that the Roman philosopher alludes not to a mirror but to a probe, the invention of which we may allow to the father of medicine, who was at first only a surgeon. When one reflects upon the use made of metal mirrors, particularly at Rome, to add to magnificence and for other purposes, and how many artists, during many successive centuries, were employed in constructing them, and vied to excel each other in their art, one cannot help conjecturing that this branch of business must at those periods have been carried to a high degree of perfection. It is therefore to be regretted that they have not been particularly described by any writer, and that on this account the art was entirely lost after the invention of glass mirrors, which are much more convenient. No one at that time entertained the least suspicion that circumstances would afterwards occur which would render these metal mirrors again necessary, as has been the case in our days by the invention of the telescope. Our artists then were obliged to make new experiments in order to discover the best mixture for mirrors of metal; and this should be a warning to mankind, never to suffer arts which have been once invented and useful to become again unknown. A circumstantial description of them should at any rate be preserved for the use of posterity, in libraries, the archives of human knowledge. When we compare metals in regard to their fitness for mirrors, we shall soon perceive that the hardest of a white colour possess in the highest degree the necessary lustre. For this reason platina is preferable to all others, as is proved from the experiments made by the Count von Sickengen. Steel approaches nearest to this new metal, and silver follows steel; but gold, copper, tin and lead, are much less endowed with the requisite property. I have however observed among the ancients no traces of steel mirrors; and it is probable they did not make any of that metal, as it is so liable to become tarnished, or to contract rust. An ancient steel-mirror is indeed said to have been once found, but as some marks of silvering were perceived on it, a question arises whether the silvered side was not properly the face of the mirror[147]. Besides, every person knows that a steel mirror would not retain its lustre many centuries amidst ruins and rubbish. The greater part of the ancient mirrors were made of silver, not on account of costliness and magnificence, as many think, but because silver, as has been said, was the fittest and the most durable of all the then known unmixed metals for that use. In the Roman code of laws, when silver plate is mentioned, under the heads of heirship and succession by propinquity, silver mirrors are rarely omitted; and Pliny[148], Seneca[149], and other writers, who inveigh against luxury, tell us, ridiculing the extravagance of the age, that every young woman in their time must have a silver mirror. These polished silver plates may however have been very slight, for all the ancient mirrors, preserved in collections, which I have ever seen, are only covered with a thin coat of that expensive metal; and in the like manner our artists have at length learned a method of making the cases of gold and silver watches so thin and light, that every footman and soldier can wear one. At first the finest silver only was employed for these mirrors, because it was imagined that they could not be made of that which was standard; but afterwards metal was used of an inferior quality. Pliny tells us so expressly, and I form the same conclusion from a passage of Plautus[150]. Philematium having taken up a mirror, the prudent Scapha gives her a towel, and desires her to wipe her fingers, lest her lover should suspect by the smell that she had been receiving money. Fine silver however communicates as little smell to the fingers as gold; but it is to be remembered that the ancients understood much better than the moderns how to discover the fineness of the noble metals by the smell, as many modes of proof which we use to find out the alloy, were to them unknown. Money-changers therefore employed their smell when they were desirous of trying the purity of coin[151]. The witty thought of Vespasian, who, when reproached on account of his tax upon urine, desired those who did so to smell the money it produced, and to tell him whether it had any smell of the article which was the object of it, alludes to this circumstance. In the like manner many savage nations at present can by their smell determine the purity of gold[152]. We are informed by Pliny, that Praxiteles, in the time of Pompey the Great, made the first silver mirror, and that mirrors of that metal were preferred to all others. Silver mirrors however were known long before that period, as is proved by the passage of Plautus above-quoted. To reconcile this contradiction, Meursius remarks that Pliny speaks only of his countrymen, and not of the Greeks, who had such articles much earlier, and the scene in Plautus is at Athens. This therefore seems to justify the account of Pliny, but of what he says afterwards I can find no explanation. Hardouin is of opinion, that mirrors, according to the newest invention, at that period, were covered behind with a plate of gold, as our mirrors are with an amalgam. But as the ancient plates of silver were not transparent, how could the gold at the back part of them produce any effect in regard to the image? May not the meaning be, that a thin plate of gold was placed at some distance before the mirror in order to throw more light upon its surface? But whatever may have been the case, Pliny himself seems not to have had much confidence in the invention. Mirrors of copper, brass and gold, I have found mentioned only by the poets, who perhaps employed the names of these metals because they best suited their measure, or because they wished to use uncommon expressions, and thought a golden mirror the noblest. By the brass ones perhaps are to be understood only such as were made of mixed copper. Did golden mirrors occur oftener, I should be inclined to refer the epithet rather to the frame or ornaments than to the mirror itself; for at present we say a gold watch, though the cases only may be of that metal. Mirrors seem for a long time to have been made of a mixture of copper and tin, as is expressly said by Pliny[153], who adds, that the best were constructed at Brundisium. This mixture, which was known to Aristotle, produces a white metal, which, on account of its colour, may have been extremely proper for the purpose, and even at present the same mixture, according to the careful experiments made by Mr. Mudge, an Englishman[154], produces the best metal for specula. It appears that the ancients had not determined the proportion very accurately; for Pliny assures us twice that in his time mirrors of silver were preferred. It is indeed not easy to ascertain the quantity of each metal that ought to be taken, and the most advantageous degree of heat; upon which a great deal depends. One of the principal difficulties is to cast the metal without blisters or air-holes, and without causing any part of the tin to oxidize, which occasions knots and cracks, and prevents it from receiving a fine polish. A passage of Lucian[155], which no one as yet has been able to clear up, alludes certainly, in my opinion, to these faults. A mixture of copper and tin is so brittle, that it is very liable to crack; and a mirror formed of it, if not preserved with great care, soon becomes so dim, that it cannot be used till it has been previously cleaned and polished. For this reason a sponge with pounded pumice-stone was generally suspended, from the ancient mirrors, and they were kept likewise in a case or box, as may be seen by the greater part of those still extant. Mirrors of silver were less subject to this inconvenience, and I am inclined to think that the latter on this account made the former be disused, as we are informed by Pliny. As ancient mirrors of metal are still to be found in collections of antiquities, it might be of some importance to the arts if chemical experiments were made on their composition. Those who have hitherto given us any account of them have contented themselves with describing their external figure and shape. Count Caylus[156] is the only person, as far as I know, who caused any chemical experiments to be undertaken on this subject. They were made on a mirror found near Naples, by M. Roux, who asserts that the composition was a mixture of copper and regulus of antimony, with a little lead. Antimony however was not known to the ancients. If that metal was really a component part, the mirror must have been the work of more modern times, or it must be allowed that the artist had metal combined with antimony without knowing it; but the latter is not probable. The experiments made by Roux do not seem to me to have proved in a satisfactory manner the presence of regulus of antimony; moreover, no certain information can be derived from them, for the antiquity of the mirror was not ascertained; nor was it known whether it ought to be reckoned amongst the best or the worst of the period when it was made. Those mirrors, which were so large that one could see one’s self in them at full length, must, in all probability, have consisted of polished plates of silver; for to cast plates of such a size of copper and tin would have required more art than we can allow to those periods; and I do not know whether our artists even now would succeed in them[157]. We read in various authors, that, besides metals, the ancients formed stones into mirrors, which were likewise in use. It is undoubtedly certain that many stones, particularly of the vitreous kind, which are opake and of a dark colour, would answer exceedingly well for that purpose; but let the choice have been ever so good, they would not, in this respect, have been nearly equal to metals. These of all mineral bodies have the most perfect opacity; and for that reason the greatest lustre: both these properties are produced by their solidity; and hence they reflect more perfectly, and with more regularity, the rays of light that proceed from other bodies. Our glass mirrors, indeed, are properly metallic. Stones, on the other hand, have at any rate some, though often hardly perceptible, transparency; so that many of the rays of light are absorbed, or at least not reflected. Mention of stone mirrors occurs also so seldom in the ancients, that we may conclude they were made rather for ornament than real utility. In general, we find accounts only of polished plates or panels of stone, fixed in the walls of wainscoted apartments, which were celebrated on account of their property of reflection. Pliny[158] praises in this respect the obsidian stone, or, as it is now called, the Icelandic agate. Everything that he says of it will be perfectly intelligible to those who are acquainted with this species of stone or vitrified lava. The image reflected from a box made of it, which I have in my possession, is like a shadow or silhouette; but with this difference, that one sees not only the contour, but also the whole figure distinctly, though the colours are darkened. To form it into images and utensils, which Pliny speaks of, must have been exceedingly difficult, on account of its brittleness. I saw at Copenhagen, among other things made of it, a drinking-cup and cover, on which the artist had been employed four years. Domitian, when he suspected that plots were formed against him, caused a gallery, in which he used to walk, to be lined with _phengites_, which by its reflection showed everything that was done behind his back[159]. Under that appellation we are undoubtedly to understand a calcareous or gypseous spar, or selenite, which is indeed capable of reflecting an image; but we cannot therefore pretend to say that the ancients formed mirrors of it; nor do I explain what Pliny says, where he speaks of the _phengites_, as if whole buildings had been once constructed of it[160]. That kind of stone, for various reasons, and particularly on account of its brittleness, is altogether unfit for such a purpose. At those periods, the windows of houses were open, and not filled up with any transparent substance, but only covered, sometimes by lattices or curtains. It is probable, therefore, that those openings of the walls of the building mentioned by Pliny, where the windows used to be, were filled up with _phengites_, which, by admitting a faint light, prevented the place from being dark even when the doors were shut; so that Pliny might say, “It appeared as if the light did not fall into the building, but as if it were inclosed in it.” I might be accused of omission did I not here mention also a passage of Pliny[161], where he seems to speak of a mirror made of an emerald, which Nero used to assist him to see the combats of the gladiators. Cary asserts that Nero was short-sighted, and that his emerald was formed like a concave lens. The former is expressly said by Pliny[162], but the latter, though by Abat considered not improbable[163], I can scarcely allow myself to believe, because such an interpretation of Pliny’s words is too forced, and because they can be explained much better in another manner. As no mention of such an excellent help to short-sighted people is to be found in any other ancient author, we must allow, if Cary’s opinion be adopted, that this property of the concave emerald was casually remarked, and that no experiments were made to cut any other natural or artificial glass in the same form for the like use, because people imagined that this property was peculiar to the emerald alone, which was then commonly supposed to be endowed with the power of greatly strengthening the eye-sight. Much more probable to me is the explanation of an Italian, which Abat also does not entirely reject, that the emerald had a smooth polished surface, and served Nero as a mirror[164]; and the passage of Pliny alluded to seems to have been thus understood by Isidore[165] and Marbodæus. It may here be objected, that real emeralds are too small to admit of being used as mirrors; but the ancients speak of some sufficiently large for that purpose, and also of artificial ones[166]; so that we may with certainty conclude, that they classed among the emeralds fluor-spar green vitrified lava, or the green Icelandic agate as it is called, green jasper, and also green glass. The piece of green glass in the monastery of Reichenau, which is seven inches in length, three inches in thickness, and weighs twenty-eight pounds three-quarters; and the large cup at Genoa, which is however full of flaws[167], have been given out to be emeralds even to the present time. Mirrors were made also of rubies, as we are assured by Pliny[168], who refers to Theophrastus for his authority; but this precious stone is never found now of such a size as to render this use possible; and Gary and the anonymous Italian before-mentioned have proved very properly that Pliny has committed a gross mistake, which has not been observed by Hardouin. Theophrastus, in the passage alluded to[169], does not speak of a ruby, but of the well-known black marble of Chio, though he calls both _carbunculus_, a name given to the ruby on account of its likeness to a burning coal, and to the black marble on account of its likeness to a quenched coal or cinder; and the latter, as well as the obsidian stone, was used sometimes for mirrors. The account how mirrors were formed by the native Americans, before they had the misfortune to become acquainted with the Europeans, is of considerable importance in the history of this art. These people had indeed mirrors which the Europeans could not help admiring. Some of them were made of black, somewhat transparent, vitrified lava, called by the Spaniards _gallinazo_, and which is of the same kind as the obsidian stone employed by the Romans for the like purpose. Of this substance the Americans had plane, concave, and convex mirrors. They had others also made of a mineral called the Inca’s stone[170], which, as has been already said by Bomare, Sage, Wallerius, and other mineralogists, was a compact pyrites or marcasite, susceptible of a fine polish; and on that account often brought to Europe, and worn formerly in rings under the name of the stone of health. Ulloa says the Inca’s stone is brittle, opake, and of a somewhat bluish colour; it has often veins which cannot be polished, and where these veins are it frequently breaks. The mirrors formed of it, which he saw, were from two to three inches in diameter; but he saw one which was a foot and a half. The opinion which some have entertained, that these mirrors were cast, has no other foundation than the likeness of polished marcasite to cast brass. This mineral is very proper for reflecting images; and I am inclined to think that the Peruvians had better mirrors than the Greeks or the Romans, among whom we find no traces of marcasite being employed in that manner. It appears, however, that the Indians had mirrors also of silver, copper, and brass[171]. I come now to the question in what century were invented our glass mirrors, which consist of a glass plate covered at the back with a thin leaf of metal. This question has been answered by some with so much confidence, that one might almost consider the point to be determined; but instead of real proofs, we find only conjectures or probabilities; and I must here remark, that I cannot help thinking that they are older than has hitherto been supposed, however desirous I may be to separate historical truth from conjecture. When I have brought together everything which I know on the subject, I would say, that attempts were even made at Sidon to form mirrors of glass; but that they must have been inferior to those of metal, because they did not banish the use of the latter. The first glass mirrors appear to me to have been of black-coloured glass, or an imitation of the obsidian stone; and to have been formed afterwards of a glass plate with some black foil placed behind it[172]. At a much later period, blown glass, while hot, was covered in the inside with lead or some metallic mixture; and still later, and, as appears, first at Murano, artists began to cover plates of glass with an amalgam of tin and quicksilver. The newest improvements are, the casting of glass-plates, and the art of making plates equally large by blowing and stretching, without the expensive and uncertain process which is required for casting. That glass mirrors were made at the celebrated glass-houses of Sidon, is mentioned so clearly by Pliny that it cannot be doubted[173]. When I read the passage, however, without prejudice, without taking into consideration what others have said on it, and compare it with what certain information the ancients, in my opinion, give on the same subject, I can understand it no otherwise than as if the author said, that the art of manufacturing glass various ways was invented, principally, at Sidon, where attempts had been made to form mirrors of it. He appears therefore to allude to experiments which had not completely succeeded; and to say that such attempts, at the time when he wrote, had been entirely abandoned and were almost forgotten. Had this circumstance formed an epoch in the art, Pliny, in another place, where he describes the various improvements of it so fully, would not have omitted it; but of those experiments he makes no further mention[174]. All the inventions which he speaks of, evidently relate to metal mirrors only, of which the silver, at that time, were the newest. Had the Sidonian mirrors consisted of glass plates covered at the back, those of metal, the making of which was, at any rate, attended with no less trouble, which were more inconvenient for use on account of their aptness to break, their requiring to be frequently cleaned and preserved in a case, and which were more unpleasant on account of the faint, dull image which they reflected, could not possibly have continued so long in use as they really did; and circumstances and expressions relative to glass mirrors must certainly have occurred. Though glass continued long to be held in high estimation, particularly at Rome; and though many kinds of glass-ware are mentioned in ancient authors, among costly pieces of furniture, mirrors are mentioned only among articles of silver plate. I am acquainted with no certain trace of glass mirrors from the time of Pliny to the thirteenth century; but after that period, at which they are spoken of in the clearest manner, we find them often mentioned in every century; and mirrors of metal at length entirely disappear. How the Sidonian mirrors were made, is not known; but if I may be allowed a conjecture, I am of opinion that they consisted of dark-coloured glass, which had a resemblance to the obsidian stone. Such is the usual progress of inventions. At those periods one had no other representation of glass mirrors than that afforded by natural glass or vitreous stones. When artists wished to make mirrors of glass, they would try to imitate the latter. After the invention of printing, people endeavoured to render printed books as like as possible to manuscripts; because they imagined that this invention was to be approved only so far as it enabled them to imitate these, without observing that it could far excel the art of writing. But the Sidonian glass mirrors were so much surpassed by the silver or brass ones, which perhaps were invented about the same time, that on this account they were never brought into use. Glass mirrors, perhaps, would have been invented sooner, had mankind employed at an earlier period glass-windows, which often, when they are shut on the outside so that no light can pass through them, reflect images in a much better manner than the best mirrors of metal. This observation, which may be made daily, would then, in all probability, have been sooner turned to advantage. No one has employed a greater profusion of words to maintain an opinion opposite to mine, than Abat; but when his proofs are divested of their ornaments, they appear so weak that one has very little inclination to agree with him. “The observation,” says he, “that a plate of glass is the best mirror, when all other rays of light, except those reflected back from the glass, are prevented, by a metallic covering placed behind it, from falling on the eye, is so easy, that it must have been made immediately after the invention of glass.” Who does not think here of Columbus and his egg? Instances occur in history of many having approached so near an invention, that we are astonished how they could have missed it; so that we may exclaim with a certain emperor, “Taurum toties non ferire difficile est[175].” “The Sidonian invention,” continues he, “would not have been worth mentioning, had it not produced better mirrors than those which the ancients had before of the obsidian stone. But these even are mentioned only once, in so short and abrupt a manner, and as it were out of ridicule, that one may easily perceive they were not much esteemed.” “If the Sidonians,” adds he, “were not the inventors, let some other inventor be mentioned;” and he assures us that he had sought information on this subject, in Neri, Kunkel, and Merret, but without success. That I believe; but Abat does not remark that by the same manner of reasoning we may ascribe to the Sidonians the invention of watches, and many other articles, the inventors of which are not to be found in books where they ought as much to be expected as the inventor of glass in Neri. The grounds on which many old commentators of the Bible, Nicholas de Lyra and others, have supposed that glass mirrors were known so early as the time of Moses, are still weaker. If quoting the names of writers who entertain a like opinion be of any weight, I could produce a much greater number of learned men, who, after an express examination of the question, deny altogether that glass mirrors were used by the ancients. Dr. Watson[176] also has endeavoured to support the opinion of Abat, but with less confidence and with more critical acumen. His grounds, I think, I have weakened already; but one observation here deserves not to be overlooked, because it suggests an idea that may serve to illustrate a passage of Pliny, which, as I before remarked, has never yet been explained. “If we admit,” says he, “that Pliny was acquainted with glass mirrors, we may thus understand what he says respecting an invention, which was then new, of applying gold behind a mirror.” Instead of an amalgam of tin, some one had proposed to cover the back of the mirror with an amalgam of gold, with which the ancients were certainly acquainted, and which they employed in gilding[177]. He mentions, also, on this occasion, that a thought had once occurred to Buffon, that an amalgam of gold might be much better for mirrors than that used at present[178]. This conjecture appears, at any rate, to be ingenious; but when I read the passage again, without prejudice, I can hardly believe that Pliny alludes to a plate of glass in a place where he speaks only of metallic mirrors; and the overlaying with amalgam requires too much art to allow me to ascribe it to such a period without sufficient proof. I consider it more probable that some person had tried, by means of a polished plate of gold, to collect the rays of light, and to throw them either on the mirror or the object, in order to render the image brighter. Professor Heeren showed me a passage in the Ecloga of Stobæus, which, on the first view, seems to allude to a glass mirror[179]. It is there said, Philolaus the Pythagorean believed that the sun was a vitreous body, which only received the rays of the æthereal fire and reflected them to us like a mirror. When we compare, however, the words of Stobæus with those by which Plutarch[180], Achilles Tatius[181], Eusebius[182], and others, express the same thing, that meaning cannot be drawn from them. It appears, at first, as if Philolaus had considered the sun to be transparent, and supposed that the rays passed through it, and came condensed to our earth, in the same manner as they are brought to a focus by a glass globe. Some commentators have explained the passage in this manner; and on account of the affinity of the Greek words have thought also of a funnel. In that case, however, the comparison of the sun with a mirror would not have been just; and if it be admitted that Philolaus considered the sun as a bright body endowed with the property of reflection, what he says of rays passing or transmitted through it, and of the pores of the sun’s body, will become unintelligible. But even if we adopt the last explanation, that Philolaus imagined the sun to be a mirror, it does not follow that he had any idea of a glass one[183]; and besides, he only speaks of a body capable of reflecting a strong light; and that glass, under certain circumstances, is fit for that purpose, may have been remarked as soon as it was invented, though men might not find out the art of forming it into proper mirrors by placing some opake substance behind it[184]. Empedocles also said, that the sun was a mirror, and that the light received by our earth was the reflection of the æthereal fire, which Eusebius compares to the reflection made by water[185]. In the problems ascribed to Alexander of Aphrodisias, glass mirrors, covered on the back with tin, are clearly mentioned; but this information does not lead us one step further in the history of the art; as it is proved that the above Alexander, who lived in the beginning of the third century, could not have written that work. The author, who must have been a physician, maintains the immortality of the soul, which Alexander of Aphrodisias, with Aristotle, denies. Some therefore have ascribed these problems to Alexander Trallianus, who practised physic in the middle of the sixth century; but this is only a conjecture which no one has as yet rendered probable, especially as there have been many physicians of the name of Alexander. The problem to which I allude is not to be found in every manuscript and edition; so that it is doubtful whether it may not be the production of a later author than that of the rest of the book, particularly as it is certain that many who had it in their possession added problems of various kinds according to their pleasure. However this may be, it is evident that the author of this problem was acquainted with mirrors covered at the back; and the expression which he uses does not merely imply that a leaf of tin was placed behind the glass plate, but that the tin in a liquid state was rubbed over it. The old French translator thinks that the author speaks of windows; but that opinion is undoubtedly false[186]. Of as little importance as the above passage of Alexander, is another of Isidore, often quoted in support of the antiquity of glass mirrors. On the first view it appears to be a testimony of great weight; but when closely examined it becomes reduced to very little. “Nothing,” says he, “is so fit for mirrors as glass[187].” Abat and others, who have considered these words as decisive, make less hesitation to ascribe to the sixth century, in which Isidore lived, a knowledge of mirrors covered on the back with tin and quicksilver, as the same writer, in another place, observes, that quicksilver can be kept in no vessel but one of glass[188]. It is very true that a glass filled with that metal will form a very good mirror; but I am of opinion that this may have been long known, before people thought of making an amalgam of tin and quicksilver in order to cover the backs of mirrors. The first passage, which is properly the one of any consequence, loses its force when we see that it is taken from Pliny and copied incorrectly. The latter says, that one can give to glass every kind of shape and colour, and that no substance is more ductile, or fitter to be moulded into any form[189]. Isidore, as is usual, says the same thing, and in the same words, except, that instead of _sequacior_ he substitutes _speculis aptior_; so that the mention of a mirror is altogether unexpected, and so little suited to what goes before and what follows, that one must believe that this alteration, occasioned perhaps by the similitude of the words, or by an abbreviation, was not made by Isidore, but by some transcriber. But even if we believe that Isidore himself spoke of glass being used at that period for mirrors, we are not able to comprehend, from what he says, how glass mirrors were made in the sixth century. I have met with no information respecting this subject in the whole period between the age of Isidore and the eleventh century. About the year 1100, at least as is supposed not without probability, Alhazen the Arabian wrote his well-known treatise on Optics, in which I conjectured that I should find mention made of glass mirrors; but I searched that work in vain, though I must confess I did not read it through entirely. Where he begins his catoptrical lessons, he however often speaks of iron mirrors, by which we may understand mirrors of the best steel. In explaining a certain phænomenon, he says, that the cause of it cannot be in the darkness of the iron mirror, because if a mirror of silver be used, the same effects will be produced. Would he not on this occasion have introduced glass mirrors, had he been as well-acquainted with them as with those already mentioned? At first, he never speaks of mirrors without adding of iron, of silver; but he mentions them afterwards without any epithet of the kind. All these mirrors I find also in the Optics of Vitello, who wrote in the middle of the thirteenth century, in Italy, a country which was at that time almost the only one where the arts flourished[190]. That author has, indeed, borrowed a great deal from Alhazen, though there are many things of his own, and he gives an account of some experiments on the refracting power of glass; but he never, as far as I have observed, mentions glass mirrors. Whether Jordanus Nemorarius, or Nemoratius, who also wrote, in the thirteenth century, a book _De Speculorum Natura_, makes mention of them, I do not know, because I have never had an opportunity of seeing that work. I am of opinion it was never printed. It is in the thirteenth century, that I find the first undoubted mention of glass mirrors covered at the back with tin or lead. Johannes Peckham, or Peccam, an English Franciscan monk, who taught at Oxford, Paris, and Rome, and who died in 1292, wrote about the year 1279 a treatise of optics, which was once printed, with the title of Johannis Pisani Perspectiva Communis[191]. In this work, besides mirrors made of iron, steel, and polished marble, the author not only speaks often of glass mirrors, but says also that they were covered on the back with lead, and that no image was reflected when the lead was scraped off. Vincentius Bellovacensis[192] speaks in a manner still clearer, for he tells us that lead was poured over the glass plate while hot. To the same century also belong the concurrent testimonies of Raimundus Lullius[193], Roger Bacon[194], Antonius di Padua[195], and Nicephorus Gregoras[196], who died after the year 1360[197]. That this invention cannot be much older we have reason to conclude, because glass mirrors were extremely scarce in France even in the fourteenth century, while mirrors of metal were in common use; and we are told that the mirror of Anne de Bretagne, consort of Louis XII., was of the latter kind[198]. Metal mirrors also were made and employed in Persia and the East, where indeed ancient usages continued longest, and glass mirrors were not known there till the commencement of the European trade with these remote regions. The former are still preferred in those countries, because they are not so liable to break, and can be preserved better in a dry hot climate than the amalgam of the latter. Respecting the progress of this art, I know nothing more than what follows:--At first, melted lead, or perhaps tin, was poured over the glass plate while yet hot as it came from the furnace. This process agrees with that which, since very early periods, has been employed in or around Nuremberg for making convex mirrors by blowing with the pipe into the glass-bubble whilst still hot a metallic mixture, with a little resin or salt of tartar, which prevents oxidation and assists the fusion. When the bubble is covered all over in the inside, and after it has cooled, it is cut into small round mirrors. This art is an old German invention, for it is described by Porta and Garzoni, who both lived in the beginning of the sixteenth century, and who both expressly say, that it was then common in Germany. Curious foreigners often attempted to learn it, and imagined that the Germans kept it a secret. Boyle made various experiments in order to discover the process; and the secretary of the Royal Society endeavoured, by means of the ambassador from Charles II., who, perhaps about 1670, resided at Frankfort, to obtain a knowledge of it; but did not succeed, as we are told by Leibnitz[199]. It was called the art of preparing mirrors without foil; and it was highly esteemed, because it was supposed that it might be useful to those fond of catoptrics, by enabling them to form convex and concave mirrors themselves. This account of Leibnitz seems to have led Von Murr into a slight error, and induced him to believe that the art of making convex mirrors without foil was first found out at Nuremberg in 1670. I introduce this remark because I flatter myself he will not be displeased that I make the above service, rendered by his native city, to be a century and a half older. These small convex mirrors, which reflect a diminished, but a clearer image than our usual mirrors, are perhaps made still, though they are not now carried round so frequently for sale in Germany as they were thirty years ago, at which time, if I remember right, they were called (_Ochsen-augen_) ox-eyes. They were set in a round painted board, and had a very broad border or margin. One of them, in my possession, is two inches and a half in diameter. It is probable that the low price of plane mirrors, when glass-houses began to be more numerous, occasioned these convex ones to be little sought after. The mixture employed in making them was, according to Porta, antimony, lead, and colophonium; but according to Garzoni, it was _una mistura di piombo, stagno, marchesita d’argento, e tartaro_, which in the German edition is translated very badly, “lead, tin, flint, silver, and tartar.” The following observation perhaps is not altogether useless: Colophonium, which is employed on many other occasions for soldering, was formerly called mirror-resin, and was sold under that name even in the beginning of the present century. Frisch assigns no reason for this appellation, and Jacobson gives a wrong one, viz. its having a bright shining surface when broken. The true reason was the above-mentioned use; and as that is now very little known, it is called from that to which it is principally applied, violin-resin. It appears that, instead of pouring melted metal over plates of glass, artists for some time applied to them the before-mentioned amalgam of tin, or covered them in some other manner, perhaps in the same way as Boyle covered concave glasses in the inside. Porta however saw almost the same process employed at Murano as that which is still followed at present. The tin, hammered to thin leaves, was spread out very smoothly; and quicksilver was poured over it, and rubbed into it, either with the hand or a hare’s foot; and when the tin was saturated it was covered with paper. The glass, wiped exceedingly clean, was then laid above it; and while the workman pressed it down with his left hand, he drew out very carefully with his right the paper that lay between the tin and the glass, over which weights were afterwards placed. This much at any rate is certain, that the method of covering with tin foil was known at Murano so early as the sixteenth century[200], and therefore it is much older than J. M. Hoffmann supposes. To conclude, whether this ingenious invention belongs to the Venetians, as several later, and particularly Italian, writers assert, I can neither prove nor contradict; but it is well known that till about the end of the seventeenth century their mirrors were sold all over Europe and in both the Indies. After that period the glass-houses in other countries were improved, and new ones established; and the discovery made in France, that glass, like metal, could be cast into much larger plates than had been before prepared by blowing and rolling, was in more than one respect prejudicial to the sale of those made at Venice. So early as the year 1634, attempts were made in France to establish glass-houses for manufacturing mirrors, and Eustache Grandmont obtained a patent for that purpose; but his undertaking was not attended with success. As Colbert exerted himself very much to promote manufactures of every kind, Nicholas de Noyer proposed to make mirrors according to the Venetian method. This plan was adopted by Charles Rivière, sieur du Freni, valet-de-chambre to the king; and having procured the royal permission, he sold it afterwards for a large sum to De Noyer, who, in 1665, received a confirmation of the patent, and an advance of 12,000 livres for four years, on condition of his procuring workmen from Venice, who, after serving eight years in the kingdom, were to be naturalized. De Noyer was joined by several more, who entered into partnership with him, and particularly by one Poquelin, who had hitherto carried on the greatest trade in Venetian mirrors, and who engaged workmen from Murano. The glass-houses were erected at the village of Tourlaville, near Cherbourg, in Lower Normandy. After the death of Colbert, who was succeeded by Louvois, the charter of the company was in 1684 renewed for thirty years longer, and at that period Pierre de Bagneux was at the head of it. Scarcely had five years of this period elapsed, when, in 1688, Abraham Thevart made a proposal to the court for casting glass mirrors of a much larger size than any ever before made. This plan, after an accurate investigation, was approved; and in the same year he received the royal permission to use his invention for thirty years, but it was not registered till 1693 or 1694. The first plates were cast at Paris, and astonished every artist who saw them. They were eighty-four inches in height, and fifty in breadth. In order to lessen the excessive expense, the glass-houses were erected at St. Gobin, in Picardy; and to prevent all dispute with the old privileged company, Thevart was expressly bound to make plates at least sixty inches in length and forty in breadth, whereas the largest of those made before had never exceeded forty-five or fifty inches in length. On the other hand, the old company were allowed to make plates of a smaller size, and were prohibited from employing any of the instruments or apparatus invented by Thevart. These however had not been so accurately defined as to remove all cause of litigation between the companies, and for that reason permission was at length granted, in 1695, for both to be united into one, under the inspection of François Plastrier, to whom the king, in 1699, sold the palace of St. Gobin. After this they declined so rapidly, that in 1701 they were not able to pay their debts, and were obliged to abandon several of the furnaces. To add to their misfortune, some of the workmen whom they had discharged retired to other countries, which were already jealous of the French invention, and wished to turn it to their advantage. The French writers assert that their attempts never succeeded, and that most of the workmen returned again to France, when a new company was formed in 1702, under the management of Antoine d’Agincourt, who by prudent œconomy improved the establishment, so as to render the profit very considerable. At present mirrors are cast as well as blown, both at St. Gobin and at Cherbourg; and in 1758 the price of them was greatly reduced, in order probably to weaken the competition of the foreign glass-houses, among which there are many not inferior to the French. This short history of the glass manufactories in France is collected from Savary[201] and Expilly[202]. A more particular account perhaps may be expected of the inventor, of his first experiments, and of their success; but notwithstanding a strict search, I have not been able to find any further information on the subject. We are told only that his name was sieur Abraham Thevart, though the historians who record that circumstance have filled their pages with uninteresting anecdotes, and even with the vices of many of the courtiers of the same period. The principal benefit which has arisen to the art from this invention, properly is, that much larger mirrors can be obtained than formerly; for when attempts were made to blow very large plates, they were always too thin. Casting, however, besides great expense in apparatus[203], requires so many expert workmen, and so tedious and severe labour, and is accompanied with so much danger, that it is only seldom that plates of an extraordinary size succeed, and the greater part of them must be cut into smaller plates which might have been blown. Those cast are never so even and smooth as those that have been blown; they require therefore a great deal of polishing, and on that account must be very thick. The monstrous mass requisite for a mirror of the largest size, stands ready melted in a very frail red-hot earthen pot, which is taken from the furnace and placed upon an iron plate, strongly heated, that the mass may be cast upon it into a glass plate. The latter must then be speedily conveyed to the cooling-furnace, and if it be found free from faults, it is ground, polished and silvered; but the last part of the process is generally done at the place where a purchaser can be found for so expensive an article, in order that less loss may be sustained in case it should happen to break by the way. These great difficulties, which have excited the astonishment of every one who has seen the process, and that of finding sale for so expensive and magnificent wares, have obliged artists to return to the old method of blowing; and many have been so fortunate in improving this branch of manufacture, that plates are formed now by blowing, sixty-four Flemish inches in height and twenty-three in breadth, which it was impossible to make before but by casting. The mass of matter necessary for this purpose, weighing more than a hundred pounds, is by the workman blown into the shape of a large bag; it is then reduced to the form of a cylinder, and being cut up, is, by stretching, rolling it with a smooth iron, and other means, transformed into an even plane. [All but the very commonest mirrors are now made of plate-glass; which is also used to a great extent for window-panes, and is manufactured by casting, rolling and polishing. The enormous plates of glass which are seen in many of the large shops of this city are well-calculated to excite the astonishment of those who are not yet aware of the late improvements in this branch of manufacture. An idea of what may be accomplished by blowing was given in 1845, at the Exhibition at Vienna, where a blown glass 7 feet in length and 3½ in breadth was exhibited; and which was of sufficient thickness to admit of polishing. Nevertheless, the casting of plate-glass is now managed with such comparative ease, that there appears to be no limit to the size to which the plates can be brought, so that the blowing of large panes of glass is given up in this country. Private houses may now be seen decorated with single sheets of glass upwards of 20 feet in height and 10 in width. A patent for a very ingenious process for silvering glass was taken out in November 1843 by Mr. Drayton. It consists in depositing silver, from a solution, upon glass, by deoxidizing the oxide of silver in solution, so that the precipitate will adhere to the glass, without the latter having been coated with metallic or other substances. This is effected by mixing 1 oz. of coarsely powdered nitrate of silver with ½ oz. of spirits of hartshorn and 2 oz. of water; after standing for 24 hours, the mixture is filtered (the deposit on the filter, which contains silver, being preserved), and an addition is made thereto of 3 oz. of spirit (by preference, spirit of wine) at 60° above proof, or naphtha; from 20 to 30 drops of oil of cassia are then added, and after remaining for about 6 hours longer, the solution is ready for use. The glass to be silvered must have a clean and polished surface; it is to be placed in a horizontal position, and a wall of putty formed around it, so that the solution may cover the surface of the glass to the depth of from ⅛th to ¼th of an inch. After the solution has been poured on the glass, from 6 to 12 drops of a mixture of oil of cloves and spirit of wine (in the proportion of 1 part by measure of the oil to 3 of spirit of wine) are dropped into it at different places; or the diluted oil of cloves may be mixed with the solution before it is poured upon the glass; the more oil of cloves used, the more rapid will be the deposition of the silver, but the patentee prefers that it should occupy about two hours. When the required deposit has been obtained, the solution is poured off; and as soon as the silver on the glass is perfectly dry, it is varnished with a composition, formed by melting together equal quantities of bees’ wax and tallow. The patentee states that, by experiment, he has ascertained that about 18 grs. of nitrate of silver are used for each square foot of glass. It has been urged as an objection to this process, that in the course of a few weeks the surfaces of the mirrors formed by it become dotted over with small brownish-red spots, which greatly injures their appearance. Dr. Stenhouse states that these spots are caused by the metallic silver, whilst being deposited on the surface of the glass, carrying down with it mechanically small quantities of a resinous matter, resulting most probably from the oxidation of the oil. This subsequently acts upon the metallic surface with which it is in contact, and produces the small brown spots already mentioned. Mr. Drayton, however, states that the brown spots only occur when the oil employed is old and unfit for use.] FOOTNOTES [135] The works in which this subject has been already treated are the following:--Eberhartus de Weihe, de Speculi origine, usu et abusu. A compilation formed without taste, of which I gave some account in the Article on Chimneys.--Spanhemii Obs. in Callimachi hymn. lavacr. Palladis, p. 615.--Académie des Inscriptions, t. xxiii. p. 140.--Recherches sur les Miroirs des Anciens, par Menard. A short paper, barren of information.--Saggi di Dissertazioni Accad. dell’ Accad. Etrusca dell’ città di Cortona, vii. p. 19: Sopra gli Specchi degli Antichi, del Sig. Cari. A translation from the French, with the figures of some ancient mirrors. It contains an explanation of some passages in Pliny, where he seems to speak of a mirror formed of a ruby, and some conjectures respecting the mirror of Nero. An anonymous member of the Academy, in an appendix, confirms the former, and considers the latter, very properly, as improbable.--Caylus, Recueil d’Antiquités, iii. p. 331, and v. p. 173. A description and figures of ancient mirrors, with some chemical experiments on their composition.--Amusemens Philosophiques. Par le père Bonaventure Abat. Amst. 1763, 8vo, p. 433: Sur l’Antiquité des Mirroirs de Verre. A dissertation worthy of being read on account of the author’s acquaintance with the ancient writers, and his knowledge of technology; but he roves beyond all proof, and employs too much verbosity to decorate his conjectures. [136] Passages of the poets, where female deities and shepherdesses are represented as contemplating themselves in water instead of a mirror, may be found in the notes to Phædri Fab. i. 4, in the edition of Burmann. [137] Chap. xxxvii. ver. 18. [138] Exodus, chap. xxxviii. ver. 8. [139] Historia Vitri apud Judæos, in Comment. Societat. Scient. Gotting. iv. p. 330. Having requested Professor Tychsen’s opinion on this subject, I received the following answer:--“You have conjectured very properly that the mirrors of the Israelitish women, mentioned Exod. xxxviii. 8, were not employed for ornamenting or covering the washing-basins, in order that the priests might behold themselves in them; but that they were melted and basins cast of them. The former was a conceit first advanced, if I am not mistaken, by Nicol. de Lyra, in the fourteenth century, and which Michaelis himself adopted in the year 1754; but he afterwards retracted his opinion when he made his translation of the Old Testament at a riper age. In the Hebrew expression there is no ground for it; and mirrors could hardly be placed very conveniently in a basin employed for washing the feet. I must at the same time confess that the word (מראת) which is here supposed to signify a mirror, occurs nowhere else in that sense. Another explanation therefore has been given, by which both the women and mirrors disappear from the passage. It is by a learned Fleming, Hermann Gid. Clement, and may be found in his Dissertatio de Labro Æneo, Groning. 1732, and also in Ugolini Thesaurus, tom. xix. p. 1505. He translates the passage thus: Fecit labrum æneum et operculum ejus æneum cum _figuris ornantibus_, quæ ornabant ostium tabernaculi. This explanation however is attended with very great difficulties; and as all the old translators and Jewish commentators have here understood mirrors; and as the common translation is perfectly agreeable to the language and circumstances, we ought to believe that Moses, not having copper, melted down the mirrors of his countrywomen and converted them into washing-basins for the priests.” [140] Oneirocrit. lib. iii. cap. 30. p. 176. [141] Joh. Sarisberiensis, i. cap. 12. [142] Plin. lib. xxxiii. cap. 9. Seneca, Quæst. Nat. i. cap. 5. [143] Vita Probi, cap. iv. p. 926: “Patinam argenteam librarum decem specillatam.” Salmasius chooses rather to read _specellatam_. I am inclined to think that this word ought to be read in Suetonius instead of _speculatum_, where he speaks of an apartment which Horace seems to have been fond of. That historian, in his Life of Horace, says, “Ad res venereas intemperantior traditur: nam _speculato_ cubiculo scorta dicitur habuisse disposita, ut quocunque respexisset, ibi ei imago coitus referretur.” Lessing, who in his Miscellanies (Vermischten Schriften, Berlin 1784, 12mo, iii. p. 205) endeavours to vindicate the poet from this aspersion, considers the expression _speculatum cubiculum_, if translated _an apartment lined with mirrors_, as contrary to the Latin idiom, and thinks therefore that the whole passage is a forgery. Baxter also before said that this anecdote had been inserted by some malicious impostor. This I will not venture to contradict, but I am of opinion that _specillatum_ or _specellatum cubiculum_ is at any rate as much agreeable to the Roman idiom as _patina specillata_. This expression Salmasius and Casaubon have justified by similar phrases, such as _opera filicata_, _tesselata_, _hederata_, &c. The chamber in which Claudian makes Venus ornament herself, and be overcome by the persuasion of Cupid, was also covered over with mirrors, so that whichever way her eyes turned, she could see her own image. Did Claudian imagine that this goddess knew how to employ such an apartment, not only for dressing, but even after she was undressed, as well as Horace? I have seen at a certain court, a bed entirely covered in the inside with mirrors. [144] Iliad. lib. xiv. ver. 166. [145] Hymnus in Lavacrum Palladis, v. 15, 21. It was however customary to ascribe a mirror to Juno, as Spanheim on this passage proves; and Athanasius, in Orat. contra Gentes, cap. xviii. p. 18, says that she was considered as the inventress of dress and all ornaments. Should not therefore the mirror, the principal instrument of dress, belong to her? May it not have been denied to her by Callimachus, because he did not find it mentioned in the description which Homer has given of her dressing-room? [146] De Natur. Deorum, iii. 22. [147] Licetus de Lucernis Antiq. lib. vi. cap. 92. [148] Lib. xxxiv. cap. 17, p. 669. [149] Quæst. Nat. at the end of the first book. [150] Mostell. act i. sc. 3. v. 101. [151] Arrianus in Epictet. i. cap. 20, p. 79. [152] Among the remaining passages of the ancients with which I am acquainted, in which mention is made of silver mirrors, the following deserves notice. Chrysostom, Serm. xvii. p. 224, who, in drawing a picture of the extravagance of the women, says, “The maid-servants must be continually importuning the silversmith to know whether their lady’s mirror be yet ready.” The best mirrors therefore were made by the silversmiths. It appears that the mirror-makers at Rome formed a particular company; at least Muratori, in Thesaur. Inscript. Clas. vii. p. 529, has made known an inscription in which _collegium speculariorum_ is mentioned. They occur also in Codex Theodos. xiii. tit. 4, 2. p. 57, where Ritter has quoted more passages in which they may be found. But perhaps the same name was given to those who covered walls with polished stones, and in latter times to glaziers. [153] Lib. xxxiii. c. 9. p. 627, and lib. xxxiv. c. 17, p. 669. [154] Philosophical Transactions, vol. lxvii. p. 296. [155] Quomodo Historia sit conscrib. cap. 51, Bipont edition, iv. p. 210, 535. Commentators have found no other way to explain κέντρον (a word which occurs in Lucian’s description of the mirror), than by the word _centre_, to which, according to their own account, there can be here no allusion. In my opinion κέντρον signifies those faulty places which are not capable of a complete polish, on account of the knots or cracks which are found in them. Lucian therefore speaks of a faultless mirror which represents the image perfect, as he afterwards informs us. [156] As the account of these experiments is given only in an expensive work, which may not often fall into the hands of those who are best able to examine it, I insert it here. “The ancient mirror, which I examined, was a metallic mixture, very tender and brittle, and of a whitish colour inclining to grey. When put into the fire, it remained a long time in a state of ignition before it melted. It was neither inflammable nor emitted any smell like garlic, which would have been the case had it contained arsenic. It did not either produce those flowers which are generally produced by all mixtures in which there is zinc. Besides, the basis of this mixture being copper, it would have been of a yellow colour had that semi-metal formed a part of it. I took two drams of it and dissolved them in the nitrous acid. A solution was speedily formed, which assumed the same colour as solutions of copper. It precipitated a white powder, which I carefully edulcorated and dried. Having put it into a crucible with a reductive flux, I obtained lead very soft and malleable. “Having filtered the solution, I took a part of it, upon which I poured an infusion of gall-nuts, but it produced no change. A solution of gold, which I poured upon another part, made it assume a beautiful green colour; but no precipitate was formed: which is sufficient to prove that there was neither iron nor tin in the mixture. “On the remaining part of the solution I poured a sufficient quantity of the volatile alkali to dissolve all the copper that might be contained in it. The solution became of a beautiful sapphire blue colour, and a white precipitate was formed. Having decanted the liquor, and carefully edulcorated the precipitate, I endeavoured to reduce it; but whether it was owing to the quantity being too small, or to my not giving it sufficient heat, I could not succeed. I had recourse therefore to another method. “I took the weight of two drams of the mixture, which I brought to a high state of ignition in a cuppel. When it was of a whitish-red colour, I threw upon it gradually four drams of sulphur, and when the flame ceased, I strengthened the fire in order to bring it to complete fusion. By these means I obtained a tender brittle regulus, whiter than the mixture, in which I observed a few small needles. Being apprehensive that some copper might still remain, I sulphurated it a second time, and then obtained a small regulus which was almost pure antimony. “It results from these experiments, that the metal of which the ancients made their mirrors was a composition of copper, regulus of antimony, and lead. Copper was the predominant, and lead the smallest part of the mixture; but it is very difficult, as is well known, to determine with any certainty the exact proportion of the substances contained in such compositions.” [In the examination of an Etruscan mirror, which was placed in my hands for analysis by Professor Gerhardt of Berlin, it was found to consist, in 100 parts, of 67·12 copper, 24·93 tin, and 8·13 lead, approximating closely to an alloy of eight parts of copper to three of tin and one of lead. The oxide of tin obtained in the course of analysis was carefully examined, before the blowpipe, for antimony, but I did not succeed in detecting a trace of that metal. A similar mirror had been likewise analysed by Klaproth; he found 62 per cent. copper, 32 tin, and 6 per cent. lead, but no trace of antimony.--W. F.] [157] Of such large mirrors Seneca speaks in his Quæst. Nat. lib. i. Of the like kind was the mirror of Demosthenes mentioned by Plutarch, Lucian, and Quintilian.--Institut. Orat. xi. 3, 68, p. 572. [158] Lib. xxxvi. c. 26, p. 758. [159] Sueton. in Vita Domit. cap. xiv. p. 334. [160] Lib. xxxvi. 22, p. 752.--“Cappadociæ lapis, duritia marmoris, candidus atque translucidus, ex quo quondam templum constructum est a quodam rege, foribus aureis, quibus clausis claritas diurna erat.”--Isidor. Origin. 16, 4. Our spar is transparent, though clouds and veins occur in it, like the violet and isabella-coloured, for example, of that found at Andreasberg. Compare this explanation with what Salmasius says in Exercitat. Plin. p. 184. [161] Lib. xxxvii. cap. 5, p. 774. [162] Lib. xi. cap. 37, p. 617. [163] This dissertation of Abat may be found translated in Neuen Hamburg. Magazin. i. p. 568. [164] Academia di Cortona, vii. p. 34. [165] Origin. xvi. 7. [166] Goguet, ii. p. 111. Fabricii Biblioth. Græca. vol. i. p. 70. [167] Keyssler, i. pp. 17 and 441. [168] Lib. xxxvii. cap. 7. [169] De Lapid. § 61. [170] [This stone acquired its name from its being much used in ornaments by the Incas or Princes of Peru.] [171] De la Vega, ii. 28. [172] Montamy in Abhandlung von den Farben zum Porzellan, Leipzig, 1767, 8vo, p. 222, asserts that he saw, in a collection of antiquities, glass mirrors which were covered behind only with a black foil. [173] Lib. xxxvi. cap. 26, p. 758. [174] Lib. xxxiii. cap. 9, p. 627. [175] Trebell. Pollio, Vita Gallien. cap. 12. [176] Chemical Essays, vol. iv. p. 246. [177] Plin. lib. xxxiii.: Æs inaurari argento vivo, aut certe hydrargyro, legitimum erat. The first name here seems to signify native quicksilver, and the second that separated from the ore by an artificial process. [178] Hist. Nat. Supplem. i. p. 451. [179] Stob. Eclog. Antv. 1575, fol. p. 56. [180] De Placitis Philos. ii. cap. 20. [181] In Aratum, cap. 19. [182] Lib. i. cap. 8. [183] It is undoubtedly certain, that ὕαλος, which is translated _vitreous_ or _glassy_, means any smooth polished body capable of reflecting rays of light. Originally it signified a watery body; and because watery bodies have a lustre, it was at length used for glass. See Salmas. ad Solin. p. 771. [184] More observations respecting the opinion of Philolaus may be found in the edition of Plutarch’s work De Placitis Philosophorum by Ed. Corsinus, Flor. 1750, 4to, p. 61, and p. 23. [185] Professor Heeren having given me his opinion on this passage of Stobæus, I shall here insert it for the satisfaction of the learned reader. The critics, says he, will hardly be persuaded that the words καὶ τὸ ἀπ’ αὐτοῦ πυροειδὲς κατὰ τὸ ἐσοπτροειδὲς are correct, as they can be translated different ways. With regard to the explanation of the matter, I build only on the plain meaning of the words. The author tells us, that Philolaus thought the sun to be a mirror; but we must conclude that he speaks of a mirror such as were then in use; a smooth plate of metal, and not a globe. In this case the first explanation of a glass globe falls to the ground. This is confirmed by Eusebius, who calls it ὑαλοειδὴς δίσκος, though it is possible that the latter word may be a gloss added by some grammarian, or by Eusebius himself. If we enter further into the explanation, we must adopt the plain idea, that the rays of the sun fall upon this plate, and are reflected to us. I am however of opinion, that ὕαλος ought to be translated _glass_, ὑαλοειδὴς _glassy_ or _vitreous_; for the intention of Philolaus evidently was to define the substance of the sun’s body. The result of the whole is, Philolaus considered the sun as a plain plate of glass which reflected the rays or brightness of the æthereal fire. But that he was acquainted with a proper glass mirror does not thence follow with certainty. [186] Pourquoy reluient les fenestres de verre si fort? Pourtant que la nature de l’estain, duquel elles sont basties par dedans, fort clere, meslée avec le verre cler aussi de lui mesme reluyst d’avantage; et le quel estain outrepassant ses raïons par les petits pores du verre, et augmentant doublement la face extérieure du dit verre, la rend grandement clere.--Problemes d’Alexandre Aphrod., traduit par M. Herret. Paris 1555, 8vo, p. 50. [187] Origin. lib. xvi. 15, p. 394. [188] Origin. lib. xvi. 18, p. 396. [189] Lib. xxxvi. cap. 26, p. 759. [190] Bayle, Diction. Histor. vol. iv. p. 462. [191] Printed at Leipzig, 1504, in small folio. There is an edition also printed at Cologne in 1624, and Fabricius quotes a Venetian edition. Pisanus seems to have been a by-name given by some one to Peckham. [192] Specul. Natur. ii. 78, p. 129. [193] Ars Magna, cap. lxvii. p. 517, in Lullii Opera. Argent. 1607, 8vo. [194] Opus Majus, ed. Jebb. Lond. 1733, fol. p. 346. [195] Franc. Assisiatis et Ant. Paduani Opera. Lugd. 1653, fol. [196] Nicephori Schol. in Synesium, in Synesii Op. Par. 1612, fol. p. 419. [197] In the collection of antiquities at St. Denis, an ancient mirror was shown, which was said to have belonged to Virgil. It was oval, and before Mabillon let it fall, was fourteen inches in length and twelve in breadth, and weighed thirty pounds. It is transparent, and of a brownish-yellow colour. According to experiments made on purpose, it was found to consist of artificial glass, mixed with a considerable portion of lead; and as it had been preserved in the above collection from the earliest periods, the practice of adding lead to glass must be very old. But whether this mirror was covered at the back, and how it was covered, though these are the most important points, I find nowhere mentioned. In the collection of the Grand Duke of Tuscany there is a piece of the same kind, said also to have been the mirror of Virgil. See Le Veil, Kunst auf Glas zu malen, Nurnb. 1779, 4to, p. 23, and Hist. de l’Acad. des Sciences, 1737, p. 412. [198] Villaret, Hist. de France. Par. 1763, xi. p. 142. [199] In Miscellanea Berolinensia, i. p. 263; but nothing further is said respecting the art, than that it was daily used in the glass-houses. Had I an opportunity, I should make experiments of every kind in order to discover a method of forming plane mirrors also in the like manner. [200] Wecker, in his book De Secretis, lib. x. p. 572, seems to say, that one must lay the saturated tin leaf so carefully on the glass plate, that no air can settle between them. According to Garzoni, the tin leaf is spread out on a smooth stone table, and after it has been rubbed over with quicksilver, the glass is placed above it. [201] Tome iii. p. 87, art. _Glace_. [202] Dict. Géog. de la France. Amst. 1762, fol. v. pp. 415, 672. [203] A furnace for casting large glass plates, before it is fit to be set at work, cost, it is said, 3500_l._ It seldom lasts above three years, and even in that time it must be repaired every six months. It takes six months to rebuild it, and three months to repair it. The melting-pots are as big as large hogsheads, and contain above 200 cwt. of metal. If one of them burst in the furnace, the loss of the matter and time amounts to 250_l._--TRANS. GLASS-CUTTING. ETCHING ON GLASS. I do not here mean to enter into the history of engraving on stone, as that subject has been already sufficiently illustrated by several men of learning well acquainted with antiquities. I shall only observe, that the ancient Greek artists formed upon glass both raised and engraved figures; as may be seen by articles still preserved in collections, though it is probable that many pieces of glass may have been moulded like paste; for that art also is of very great antiquity[204]. It appears likewise that they cut upon plates of glass and hollow glass vessels all kinds of figures and ornaments, in the same manner as names, coats of arms, flowers, landscapes, &c. are cut upon drinking-glasses at present[205]. If we can believe that learned engraver in stone, the celebrated Natter, the ancients employed the same kind of instruments for this purpose as those used by the moderns[206]. They undoubtedly had in like manner a wheel which moved round in a horizontal direction above the work-table, or that machine which by writers is called a lapidary’s wheel. If this conjecture be true, what Pliny says respecting the various ways of preparing glass is perfectly intelligible. It is turned, says he, by the wheel, and engraven like silver. In my opinion we are to understand by the first part of this sentence, that the glass was cut by the wheel, like stone, both hollow and in relief, though it is possible that drinking-cups or vessels may have been formed from the glass metal by means of the wheel also[207]. In the latter part of the sentence we must not imagine that Pliny alludes to gravers like those used by silversmiths, for the comparison will not apply to instruments or to the manner of working, which in silver and glass must be totally different; but to the figures delineated on the former, which were only cut out on the surface in a shallow manner; and such figures were formed on glass by the ancient artists, as they are by our glass-cutters, by means of a wheel. Many, however, affirm that the art of glass-cutting, together with the necessary instruments, was first invented in the beginning of the seventeenth century. The inventor is said to have been Casper Lehmann, who originally was a cutter of steel and iron; and who made an attempt, which succeeded, of cutting crystal, and afterwards glass, in the like manner. He was in the service of the emperor Rodolphus II., who, in the year 1609, besides presents, conferred on him the title of lapidary and glass-cutter to the court, and gave him a patent by which every one except himself was forbidden to exercise this new art. He worked at Prague, where he had an assistant named Zacharias Belzer; but George Schwanhard the elder, one of his scholars, carried on the same business to a far greater extent. The latter, who was a son of Hans Schwanhard, a joiner at Rothenburg, was born in 1601; and in 1618 went to Prague to learn the art of glass-cutting from Lehmann. By his good behaviour he so much gained the esteem of his master, who died a bachelor in 1622, that he was left his heir; and obtained from the emperor Rodolphus a continuation of Lehmann’s patent. Schwanhard, however, removed to Nuremberg, where he worked for many of the principal nobility; and by these means procured to that city the honour of being accounted the birth-place of this new art. In the year 1652 he worked at Prague and Ratisbon by command of the emperor Ferdinand III., and died in 1667, leaving behind him two sons, who both followed the occupation of the father. The elder, who had the same christian name as the father, died so early as 1676; but the other, Henry, survived him several years. After that period Nuremberg produced in this art more expert masters, who, by improving the tools and devising cheaper methods of employing them, brought it to a much higher degree of perfection[208]. That the art is of so modern date seems to be confirmed by Zahn, who speaks of it as of a new employment carried on at that time, particularly at Nuremberg. He describes the work-table as well as the other instruments; and gives a figure of the whole, which he appears to have considered as the first[209]. It may be seen, however, from what I have already quoted, that this invention does not belong entirely to the moderns; and, to deny that the ancients were altogether unacquainted with it, would be doing them an injustice. It was forgotten and again revived; and this is the opinion of Caylus. I must here remark, that before this invention there were artists, who, with a diamond, cut or engraved figures on glass, which were everywhere admired. Without entering, however, into the history of diamonds, which would require more materials than I have yet been able to collect, I will venture to assert that the ancient artists employed diamond dust for polishing or cutting other kinds of stones. Pliny[210] speaks of this in so clear a manner that it cannot be doubted. The same thing has been repeated by Solinus[211], Isidore[212], and Albertus Magnus[213], in a manner equally clear, and Mariette[214] considers it as fully proved; but it does not appear that the ancients made any attempts to cut this precious stone with its own dust; I mean to give it different faces and to render it brilliant. Whether they engraved on it in that manner I cannot pretend to decide, as the greatest artists are not agreed on the subject. Mariette[215] denies that they did; whereas Natter[216] seems not to deny it altogether, and Klotz[217] confidently asserts it as a thing certain. But the last-mentioned author knew nothing more of this circumstance than what he had read in the above-quoted writers. The question which properly belongs to my subject is, whether the Greeks and the Romans used diamond pencils for engraving on other stones. That many ancient artists assisted their labour by them, or gave their work the finishing touches, seems, according to Natter, to be shown by various antique gems. But even allowing this to have been the case (for at any rate I dare not contradict so eminent a connoisseur), I must confess that I have found no proofs that the ancients cut glass with a diamond. We are however acquainted with the means employed by the old glaziers to cut glass: they used for that purpose emery, sharp-pointed instruments of the hardest steel, and a red-hot iron, by which they directed the rents according to their pleasure. The first mention of a diamond being used for writing on glass occurs in the sixteenth century. Francis I. of France, who was fond of the arts, sciences, and new inventions, wrote the following lines with his diamond ring upon a pane of glass, at the castle of Chambord, in order to let Anne de Pisseleu, duchess of Estampes, know that he was jealous: Souvent femme varie, Mal habil qui s’y fie. The historian recorded this not so much on account of the admonition, which is not new, as because it was then thought very ingenious to write upon glass[218]. About the year 1562, festoons and other ornaments, cut with a diamond, were extremely common on Venetian glasses, which at that period were accounted the best. George Schwanhard the elder was a great master in this art[219]; and in more modern times, John Rost, an artist of Augsburg, ornamented in a very curious manner with a diamond pencil, some drinking-glasses which were purchased by the emperor Charles VI. I now come to the art of etching on glass, which properly was the subject of this article. As the acid which dissolves siliceous earth, and also glass, was first discovered in the year 1771, by Scheele the chemist[220], in fluor-spar, one might imagine that the art of engraving with it upon glass could not be older. It has indeed been announced by many as a new invention[221]; but it can be proved that it was discovered as early as the year 1670, by the before-mentioned artist Henry Schwanhard. We are told that some aquafortis having fallen by accident upon his spectacles, the glass was corroded by it; and that he thence learned to make a liquid by which he could etch writing and figures upon plates of glass[222]. How Schwanhard prepared this liquid I find nowhere mentioned; but at present we are acquainted with no other acid but that of fluor-spar which will corrode every kind of glass; and it is very probable that his preparation was the same as that known to some artists as a secret in 1721. The inventor however employed it to a purpose different from that for which it is used at present. At present the glass is covered with a varnish, and those figures which one intends to etch are traced out through it; but Schwanhard, when the figures were formed, covered them with varnish, and then by his liquid corroded the glass around them; so that the figures, which remained smooth and clear, appeared when the varnish was removed, raised from a dim or dark ground. He perhaps adopted this method in order to render his invention different from the art known long before of cutting the figures on the glass as if engraven. Had he been able to investigate properly what accident presented to him, he might have enriched the arts with a discovery which gave great reputation to a chemist a hundred years after. I mentioned this old method of etching in relief to our ingenious Klindworth, who possesses great dexterity in such arts, and requested him to try it. He drew a tree with oil varnish and colours on a plate of glass, applied the acid to the plate in the usual manner, and then removed the varnish. By these means a bright, smooth figure was produced upon a dim ground, which had a much better effect than those figures that are cut into the glass. I recommend this process, because I am of opinion that it may be brought to much greater perfection; and M. Renard, that celebrated artist of Strasburg, whose thermometers with glass scales, in which the degrees and numbers are etched, have met with universal approbation, was of the same opinion, when I mentioned the method to him while he resided here, banished from his home by the disturbances in his native country. It is probable that Schwanhard and his scholars kept the preparation of this liquid a secret, as the receipt for that purpose was not made known till the year 1725, though it is possible that one older may be found in some of those books which treat on the arts. In the above-mentioned year, Dr. John George Weygand, from Goldingen in Courland, sent to the editor of a periodical work a receipt which had been written out for him by Dr. Matth. Pauli of Dresden, then deceased, who had etched, in this manner on glass, arms, landscapes, and figures of various kinds[223]. We find by it that a strong acid of nitre was used, which certainly disengages the acid of fluor-spar, though the vitriolic acid is commonly employed for that purpose[224]. That the Bohemian emerald or _hesphorus_, mentioned in the receipt, is green fluor-spar, cannot be doubted, and will appear still more certain from the history of this species of stone, as far as I am acquainted with it, which I shall here insert. In the works of the old mineralogists, fluor-spar is either not mentioned, or is classed among their natural glasses and precious stones; and in those of the first systematic writers it is so mingled with quartz and calcareous and gypseous spars, that it is impossible to discover it. The old German miners, however, distinguished it so early as the sixteenth century, and called it _fluss_; because they used it to accelerate the fusion of ores that were difficult to be reduced to that state. Agricola, who first remarked this, changed the German name into _fluor_, an appellation, which, like many others, formed by him from German words, such for example as _quarzum_ from _quarz_, _spatum_ from _spat_, _wismuthum_, _zincum_, _cobaltum_, &c., became afterwards common. If a passage of the ancients can be quoted that seems to allude to fluor-spar, it is that of Theophrastus, where he says that there are certain stones which, when added to silver, copper, and iron ores, become fluid[225]. The first systematic writer who mentioned this kind of stone as a particular genus, was Cronstedt. Besides being known by its metallurgic use, fluor-spar is known also by having the colours of some precious stones, so that it may be sold, or at least shown as such to those who are not expert judges; because the first time when heated in the dark it shines with a bluish-green lustre. It is possible that fluor-spar may have been among the number of that great variety of stones which the ancients, with much astonishment, tell us shone in the dark; though it is certain that the principal part of them were only light-magnets, as they are called, or such as retain for a certain period the light they have absorbed in the day-time. The observation, however, that fluor-spar emits light after it is heated, seems to have been first made when artificial phosphorus excited the inquiry of naturalists and chemists; and when they began to search in their own country for stones which, in the property of emitting light, might have a resemblance to the Bologna spar, made known about the year 1630. It is well known that the latter is prepared for that purpose by calcination. Stones of the like kind were sought for; and among these fluor-spar, which is not scarce in Germany. In my opinion, the observation was made in the year 1676; for in that year Elsholz informed the members of the Society for investigating Nature, that he was acquainted with a phosphorus which had its light neither from the sun nor from fire, but which, when heated on a metal plate over glowing coals, shone with a bluish-white lustre; so that by strewing the powder of it over paper, one might form luminous writing. I doubt much whether this experiment was ever tried; at least I find no further account of it in the papers of the Society, nor in the re-publication of the above author’s first dissertation, which appeared in 1681[226]. As far as I know, Kirchmaier, professor at Wittenberg, was the first who disclosed the secret, in the year 1679[227]. Both call this phosphorus the smaragdine; because the ancients speak much of luminous emeralds, and because green fluor-spar is often exhibited as an emerald. Kirchmaier calls this mineral also _hesperus_ and _vesperugo_; and these names have been often given since to fluor-spar, as in the receipt before-mentioned for making a liquid to etch on glass. Kirchmaier’s information, however, must have been very little known; for the Jesuit Casatus, who, in 1684, wrote his Treatise on Fire, was not acquainted with it, as he has inserted only the words of Elsholz. This observation must have been new to Leibnitz himself, and to the Academy of Sciences at Berlin, in 1710; for the former then mentioned it to the Society as a philosophical novelty[228]. I shall remark, in the last place, that the manufacturing of vessels and ornaments of every kind from solid fluor-spar was begun in Derbyshire in the year 1765[229]. The articles formed of it are in England called spar ornaments, and sometimes _blue John_. Many beautiful colours must, as is said, be brought forward by means of fire. But the heat must be applied with great caution; for fluor-spar, as is well known, by a strong and particularly a sudden heating, cracks, and loses its transparency. Since writing the above, I find that M. Raspe[230] denies this bringing forward of colours by fire. FOOTNOTES [204] Mariette, Traité des Pierres gravées. Par. 1750, fol. [205] The two ancient glasses found at Nismes, and described in Caylus’ Recueil d’Antiquités, ii. p. 363, were probably of this sort. [206] Natter, Traité de la Méthode antique de graver en Pierres fines, comparé avec la Méthode moderne. Lond. 1754, fol. [207] Of this kind were the _calices audaces_ of Martial, xiv. 94, and those cups which often broke when the artist wished to give them the finishing touch. [208] See Sandrart’s Teutsche Akademie, vol. i. part 2, p. 345, where there is much valuable information respecting the German artists. Compare also Doppelmayer’s Nachricht von Nürnberg. Künstlern. [209] Oculus Artificial. iii. p. 79. [210] Lib. xxxvii. [211] Cap. 52, p. 59. [212] Origin. xvi. 8. [213] De Miner. lib. ii. 2. [214] Traité des Pierres gravées, i. pp. 90, 156. [215] Ibid. p. 156. [216] In the preface, p. 15. [217] Ueber den Nutzen d. geschnitt. Steine. Altenb. 1768, p. 42. [218] Le Veil, iii. p. 19. This anecdote however is not mentioned by Mezeray, Castelnau, or Laboureur; and Bayle must have been unacquainted with it, or he would have introduced it into his long article on the Duchesse d’Estampes. [219] Doppelmayer, p. 232. [220] Abhandlungen der Schwed. Akad. xxxiii. p. 122. [221] Halle, Fortgesetzte Magie. Berlin, 1788, 8vo, i. p. 516. This author says that the invention came from England, where it was kept very secret; but the honour of the second invention belongs to H. Klaproth. [222] Schwanhard, by the acuteness of his genius, proved what was before considered as impossible, and found out a corrosive so powerful that the hardest crystal glass, which had hitherto withstood the force of the strongest spirits, was obliged to yield to it, as well as metals and stones. By these means he delineated and etched on glass, figures of men, some naked and some dressed, and all kinds of animals, flowers, and plants, in a manner perfectly natural; and brought them into the highest estimation.--Sandrart, Teutsche Akademie, i. 2, p. 346.--Doppelmayer, p. 250, says, “After 1670 he accidentally found out by the glass of his spectacles, upon which some aquafortis had fallen, becoming quite soft, the art of etching on glass.” [223] Breslauer Sammlung zur Natur- und Medicin-Geschichte. 1725, January, p. 107. “Invention of a powerful acid by which figures of every kind, according to fancy, can be etched upon glass.--When _spiritus nitri per distillationem_ has passed into the recipient, ply it with a strong fire, and when well dephlegmated, pour it, as it corrodes ordinary glass, into a Waldenburg flask; then throw into it a pulverised green Bohemian emerald, otherwise called _hesphorus_ (which, when reduced to powder and heated, emits in the dark a green light), and place it in warm sand for twenty-four hours. Take a piece of glass well cleaned and freed from all grease by means of a lye; put a border of wax round it, about an inch in height, and cover it all equally over with the above acid. The longer you let it stand the better, and at the end of some time the glass will be corroded, and the figures, which have been traced out with sulphur and varnish, will appear as if raised above the plane of the glass.” This receipt has been inserted by H. Krunitz in his Œkonomische Encyclopedie, xi. p. 678. [224] Klindworth covers the glass with the etching ground of the engravers; but in the Annals of Chemistry for 1790, ii. p. 141, a solution of isinglass in water, or a turpentine oil varnish, mixed with a little white lead, is recommended. Complete instructions for acquiring this art may be found there also. [225] De Lapidibus, sect. 19. [226] See Ephemerid. ac Nat. Cur. 1676, Dec. 1, obs. 13, p. 32; and Elsholtii De Phosphoris Observationes, Berol. 1681, 4to. [227] G. C. Kirchmaieri De Phosphoris et Natura Lucis, necnon de Igne, Commentatio Epistolica. Wittebergæ, 1680, 4to. [228] Miscellanea Berolin. 1710, vol. i. p. 97. The fluor-spar earth, or phosphoric earth, as it is called, which in later times has been found in marble quarries, and which some at present consider as an earth saturated with phosphoric acid, is mentioned by the Swede Hierne, in Prodromus Hist. Nat. Sueciæ. Henkel had never seen it. [229] Watson’s Chemical Essays, ii. p. 277. [230] Descriptive Catalogue of Tassie’s Engraved Gems, Lond. 1791, 2 vols. 4to, i. p. 51. SOAP. That the first express mention of soap occurs in Pliny and Galen, and that the former declares it to be an invention of the Gauls, though he prefers the German to the Gallic soap[231], has already been remarked by many. Pliny says that soap[232] was made of tallow and ashes; that the best was made of goats’ tallow and the ashes of the beech-tree, and that there were two kinds of it, hard and soft. The author of a work on simple medicines, which is ascribed to Galen, but which however does not seem to have been written by that author, and of which only a Latin translation has been printed, speaks of soap being made by a mixture of oxen, goats’, or sheep’s tallow, and a lye of ashes strengthened with quicklime. He says the German soap was the purest, the fattest, and the best, and that the next in quality was the Gallic[233]. This account corresponds more exactly with the process used in Germany at present; whereas the French use mineral alkali, and instead of tallow, employ oil, which appears to be a later invention. Pliny in his description does not speak of quicklime; but as he mentions a mixture of goats’ tallow and quicklime a little before, it is probable that the use of the latter was then known at Rome. Gallic and German soap are often mentioned by later writers[234], as well as by the Arabians, sometimes on account of their external use as a medicine, and sometimes on account of their use in washing clothes. The latter purpose is that for which soap is principally employed in modern times; but it does not seem to have been the cause of German soap being introduced at Rome. Washing there was the occupation of indigent scourers, who did not give themselves much trouble concerning foreign commodities. The German soap, with which, as Pliny tells us, the Germans coloured their hair red, was imported to Rome for the use of the fashionable Roman ladies and their gallants. There is no doubt that the _pilæ Mattiacæ_, which Martial recommends as a preventive of gray hair[235]; the _caustica spuma_ with which the Germans dyed their hair[236]; and the Batavian froth or lather which the Romans employed for colouring theirs[237], were German soap. It is probable that the Germans tinged it with those plants which were sent to Rome for dyeing the hair[238]; and according to the modern manner of speaking, it was more properly a kind of pomade than soap. It appears that the Romans at first considered hair-soap as an ointment made from ashes; for we read in various passages of ancient authors, that the hair was dyed by means of ashes, or an ointment made of ashes and a certain kind of oil. It is however possible that they may have had such an ointment, which undoubtedly would be of a saponaceous nature, before they were acquainted with the German soap, or that they imitated the German pomade with different variations[239]. As soap is everywhere used for washing at present, a question arises what substitutes were employed before it was invented. Those with which I am acquainted I shall mention and endeavour to illustrate. They are all still used, though not in general; and they are all of a soapy nature, or at least have the same effects as soap; so that we may say the ancients used soap without knowing it. Our soap is produced by a mixture of lixivious salts and tallow, by which means the latter becomes soluble in water. The greater part of the dirt on our linen and clothes consists of oily perspiration or grease, or dust which that grease attracts, and which either cannot be washed out, or, but very imperfectly, by water alone. But if warm water, to which lixivious salts have in any manner been added, be taken, and if dirty cloth be rubbed in it, the greasy dirt unites with the salts, becomes saponaceous, and is so far soluble in water that it may be washed out. There are also natural juices which are of a soapy quality, in the state in which we find them, and which can be employed in the stead of artificial soap. Of this kind is the gall of animals and the sap of many plants. The former being less strong in its effects on account of its slimy nature, is used at present particularly for coloured stuffs, the dye of which is apt to fade. As far as I know, however, it was not employed by the ancients[240], but it is certain that in washing they used saponaceous plants. In the remotest periods it appears that clothes were cleaned by being rubbed or stamped upon in water, without the addition of any substance whatever. We are told by Homer, that Nausicaa and her attendants washed their clothes by treading upon them with their feet in pits, into which they had collected water[241]. The epithet black, which the poet gives to the water, might induce one to conjecture that it had been mixed with ashes, which would convert it into a lye; but where were the ashes to be found? Had they brought them along with them, the bard, where he before enumerates everything that they carried with them, and even oil, would not have failed to mention them; and such a conjecture is rendered entirely groundless by his applying the same epithet to pure water, in other places, where nothing can be supposed to have coloured it[242]. Water, when it stands in deep pits, reflects so few rays of light, that in a poetical sense it may very properly be called black. We find however mention made at later periods of ashes, and a lye of ashes employed for washing; but I think very seldom, and I do not know how old the use of them may be. According to Julius Pollux, _konia_, mentioned by Aristophanes and Plato, was a substance used for washing; and he says expressly, that we are to understand by it a lye of ashes. This I mention for the sake of those, who, like me, place little confidence in the terms of art given in dictionaries. With the above lye, oil- and wine-jars were cleaned[243]; and it was employed also for washing the images of the gods[244]. The method of strengthening the lye by means of unslaked lime was known, at any rate, in the time of Paulus Ægineta; but it appears that the Romans were not acquainted with the salt itself, which is procured by dissolving common wood-ashes in water: I mean, they did not understand the art of producing it in a dry solid form, or of boiling potashes. On the other hand, that fixed lixivious salt, the mineral which nature presents in many of the southern countries, was long known and used in washing. This was the _nitrum_, or, as the people of Attica pronounced it, the _litrum_, of the ancients, as has already been remarked by others[245]. It would however be worth the trouble to investigate the proofs still further. By examining them with more mineralogical and chemical knowledge than have hitherto been employed for that purpose, they might be further strengthened, and serve to illustrate many obscure passages. For my part, I have neither leisure nor room here to undertake such a task, though I have collected many observations relative to that subject. It is certain at any rate, that the ancients employed _nitrum_ for washing, and it is evident from the testimony of various authors, that it was much used in the baths[246]. That the people of Egypt, in the time of Pliny, made mineral alkali also from the ashes of some plants, we have reason to conclude, because he says that it was necessary to put the Egyptian nitre into vessels well-corked, else it became liquid. Natural alkali is never liable to do so, unless it be very much burnt; and as no reason is assigned for its assuming that form, we may believe that the Egyptian alkali was the strongly burnt ashes of those plants which are still used in Egypt for making salt, and perhaps the same with which the Spaniards were made acquainted by the Arabians, and which they cultivate for making soda. Strabo speaks of an alkaline water in Armenia, which was used by the scourers for washing clothes[247]. Of this kind also must have been the lake Ascanius, which is mentioned by Aristotle[248], Antigonus Carystius[249], and Pliny[250]. It is worthy of remark, that the ancients made ointments of this mineral alkali and oil, but not hard soap, though by these means they approached nearer to the invention than the old Germans in their use of wood-ashes; for dry solid soap can be made with more ease from the mineral than the vegetable alkali; and when Hungarian, French, and German soap are of equal goodness, the last does more credit to the manufacturers because they cannot employ the mineral alkali. I shall here observe, that this alkali was used for washing by the Hebrews, and that it occurs in the sacred writings under the name of _borith_[251]. The cheapest however, and the most common article used for washing, was the urine of men and animals. When this excrement becomes old, the alkali disengages itself, which may be perceived by its fœtid smell; and such alkalised urine being warmed, and employed to wash greasy clothes, produces the same effects as the _nitrum_ of the ancients. It is still used for the like purpose in our cloth manufactories. To procure a supply of it, the ancient washers and scourers placed at the corners of the streets, vessels which they carried away after they had been filled by the passengers, who were at liberty to use them; and the practice of having such conveniences was certainly more decent than that of employing the walls of churches and other buildings, which the police of Dresden forbade some years ago, but with no effect. At Rome, that which at present spoils and renders filthy our noblest edifices, was converted to use. When clothes were washed, they were trod upon with the feet, as was the case in the cloth manufactories at Leeds, Halifax, and other places of England, where the urine was collected by servants, and sold by measure to the manufacturers under the name of _old lant_. On account of the disagreeable smell attending their employment, scourers at Rome were obliged to reside either in the suburbs or in some of the unfrequented streets[252]. My readers here will undoubtedly call to remembrance the source of taxation devised by the emperor Vespasian, who, as his historians tell us, _urinæ vectigal commentus est_[253]. It is not certainly known in what manner this impost was regulated. Did the emperor declare that article, which was not _subterraneum rarius_, to be a regale as a _res derelicta_, so that the scourers were obliged to pay him what he thought a reasonable sum proportioned to the benefit which they derived from it? Or was it imposed only as a poll-tax? For every tax upon anything indispensably necessary to all, is, to speak in the language of finance, the same as what is called a poll-tax, or a tax paid by every one who has a head. The latter conjecture is the most probable, especially as this tax continued two centuries, till the time of Anastasius, and as we read also of _vectigal pro urina jumentorum et canum_, which was exacted from every person who kept cattle. Vespasian therefore was not fortunate in the choice of a name for his tribute, which on that account must have been undoubtedly more detested. A poll-tax at present is called by those who do not speak favourably of it, the Turkish-tax, because the Turks impose it on all unbelievers. When it was introduced by Louis XIV. in 1695, he called it _la capitation_. Of plants with a saponaceous juice, the ancients, at any rate, used one instead of soap; but it is difficult or rather impossible to define it. I shall not therefore content myself merely with transcribing the passages where it is mentioned, but I shall arrange whatever I can find respecting it in such a manner, as, according to my opinion, the names of plants ought to be explained in dictionaries. Στρουθίον, Struthium, Latinis Herba lanaria, et Plinio etiam Radicula.