Book VI.

[14] Fire-setting as an aid to breaking rock is of very ancient origin, and moreover it persisted in certain German and Norwegian mines down to the end of the 19th century--270 years after the first application of explosives to mining. The first specific reference to fire-setting in mining is by Agatharchides (2nd century B.C.) whose works are not extant, but who is quoted by both Diodorus Siculus and Photius, for which statement see note 8, p. 279. Pliny (XXXIII, 21) says: "Occasionally a kind of silex is met with, which must be broken with fire and vinegar, or as the tunnels are filled with suffocating fumes and smoke, they frequently use bruising machines, carrying 150 _librae_ of iron." This combination of fire and vinegar he again refers to (XXIII, 27), where he dilates in the same sentence on the usefulness of vinegar for breaking rock and for salad dressing. This myth about breaking rocks with fire and vinegar is of more than usual interest, and its origin seems to be in the legend that Hannibal thus broke through the Alps. Livy (59 B.C., 17 A.D.) seems to be the first to produce this myth in writing; and, in any event, by Pliny's time (23-79 A.D.) it had become an established method--in literature. Livy (XXI, 37) says, in connection with Hannibal's crossing of the Alps: "They set fire to it (the timber) when a wind had arisen suitable to excite the fire, then when the rock was hot it was crumbled by pouring on vinegar (_infuso aceto_). In this manner the cliff heated by the fire was broken by iron tools, and the declivities eased by turnings, so that not only the beasts of burden but also the elephants could be led down." Hannibal crossed the Alps in 218 B.C. and Livy's account was written 200 years later, by which time Hannibal's memory among the Romans was generally surrounded by Herculean fables. Be this as it may, by Pliny's time the vinegar was generally accepted, and has been ceaselessly debated ever since. Nor has the myth ceased to grow, despite the remarks of Gibbon, Lavalette, and others. A recent historian (Hennebert, _Histoire d' Annibal_ II, p. 253) of that famous engineer and soldier, soberly sets out to prove that inasmuch as literal acceptance of ordinary vinegar is impossible, the Phoenicians must have possessed some mysterious high explosive. A still more recent biographer swallows this argument _in toto_. (Morris, "Hannibal," London, 1903, p. 103). A study of the commentators of this passage, although it would fill a volume with sterile words, would disclose one generalization: That the real scholars have passed over the passage with the comment that it is either a corruption or an old woman's tale, but that hosts of soldiers who set about the biography of famous generals and campaigns, almost to a man take the passage seriously, and seriously explain it by way of the rock being limestone, or snow, or by the use of explosives, or other foolishness. It has been proposed, although there are grammatical objections, that the text is slightly corrupt and read _infosso acuto_, instead of _infuso aceto_, in which case all becomes easy from a mining point of view. If so, however, it must be assumed that the corruption occurred during the 20 years between Livy and Pliny. By the use of fire-setting in recent times at Koenigsberg (Arthur L. Collins, "Fire-setting," Federated Inst. of Mining Engineers, Vol. V, p. 82) an advance of from 5 to 20 feet per month in headings was accomplished, and on the score of economy survived the use of gunpowder, but has now been abandoned in favour of dynamite. We may mention that the use of gunpowder for blasting was first introduced at Schemnitz by Caspar Weindle, in 1627, but apparently was not introduced into English mines for nearly 75 years afterward, as the late 17th century English writers continue to describe fire-setting. [15] The strata here enumerated are given in the Glossary of _De Re Metallica_ as follows:-- _Corium terrae_ _Die erd oder leim._ _Saxum rubrum_ _Rot gebirge._ _Alterum item rubrum_ _Roterkle._ _Argilla cinerea_ _Thone._ _Tertium saxum_ _Gerhulle._ _Cineris vena_ _Asche._ _Quartum saxum_ _Gniest._ _Quintum saxum_ _Schwehlen._ _Sextum saxum_ _Oberrauchstein._ _Septimum saxum_ _Zechstein._ _Octavum saxum_ _Underrauchstein._ _Nonum saxum_ _Blitterstein._ _Decimum saxum_ _Oberschuelen._ _Undecimum saxum_ _Mittelstein._ _Duodecimum saxum_ _Underschuelen._ _Decimumtertium saxum_ _Dach._ _Decimumquartum saxum_ _Norweg._ _Decimumquintum saxum_ _Lotwerg._ _Decimumsextum saxum_ _Kamme._ _Lapis aerosus fissilis_ _Schifer._ The description is no doubt that of the Mannsfeld cupriferous slates. It is of some additional interest as the first attempt at stratigraphic distinctions, although this must not be taken too literally, for we have rendered the different numbered "_saxum_" in this connection as "stratum." The German terms given by Agricola above, can many of them be identified in the miners' terms to-day for the various strata at Mannsfeld. Over the _kupferschiefer_ the names to-day are _kammschale_, _dach_, _faule_, _zechstein_, _rauchwacke_, _rauchstein_, _asche_. The relative thickness of these beds is much the same as given by Agricola. The stringers in the 8th stratum of stone, which fuse in the fire of the second order, were possibly calcite. The _rauchstein_ of the modern section is distinguished by stringers of calcite, which give it at times a brecciated appearance. [16] The history of surveying and surveying instruments, and in a subsidiary way their application to mine work, is a subject upon which there exists a most extensive literature. However, that portion of such history which relates to the period prior to Agricola represents a much less proportion of the whole than do the citations to this chapter in _De Re Metallica_, which is the first comprehensive discussion of the mining application. The history of such instruments is too extensive to be entered upon in a footnote, but there are some fundamental considerations which, if they had been present in the minds of historical students of this subject, would have considerably abridged the literature on it. First, there can be no doubt that measuring cords or rods and boundary stones existed almost from the first division of land. There is, therefore, no need to try to discover their origins. Second, the history of surveying and surveying instruments really begins with the invention of instruments for taking levels, or for the determination of angles with a view to geometrical calculation. The meagre facts bearing upon this subject do not warrant the endless expansion they have received by argument as to what was probable, in order to accomplish assumed methods of construction among the Ancients. For instance, the argument that in carrying the Grand Canal over watersheds with necessary reservoir supply, the Chinese must have had accurate levelling and surveying instruments before the Christian Era, and must have conceived in advance a completed work, does not hold water when any investigation will demonstrate that the canal grew by slow accretion from the lateral river systems, until it joined almost by accident. Much the same may be said about the preconception of engineering results in several other ancient works. There can be no certainty as to who first invented instruments of the order mentioned above; for instance, the invention of the dioptra has been ascribed to Hero, _vide_ his work on the _Dioptra_. He has been assumed to have lived in the 1st or 2nd Century B.C. Recent investigations, however, have shown that he lived about 100 A.D. (Sir Thomas Heath, Encyc. Brit. 11th Ed., XIII, 378). As this instrument is mentioned by Vitruvius (50 -0 B.C.) the myth that Hero was the inventor must also disappear. Incidentally Vitruvius (VIII, 5) describes a levelling instrument called a _chorobates_, which was a frame levelled either by a groove of water or by plumb strings. Be the inventor of the _dioptra_ who he may, Hero's work on that subject contains the first suggestion of mine surveys in the problems (XIII, XIV, XV, XVI), where geometrical methods are elucidated for determining the depths required for the connection of shafts and tunnels. On the compass we give further notes on p. 56. It was probably an evolution of the 13th Century. As to the application of angle- and level-determining instruments to underground surveys, so far as we know there is no reference prior to Agricola, except that of Hero. Mr. Bennett Brough (Cantor Lecture, London, 1892) points out that the _Nuetzliche Bergbuechlin_ (see Appendix) describes a mine compass, but there is not the slightest reference to its use for anything but surface direction of veins. Although map-making of a primitive sort requires no instruments, except legs, the oldest map in the world possesses unusual interest because it happens to be a map of a mining region. This well-known Turin papyrus dates from Seti I. (about 1300 B.C.), and it represents certain gold mines between the Nile and the Red Sea. The best discussion is by Chabas (_Inscriptions des Mines d'Or_, Chalons-sur-Saone, Paris, 1862, p. 30-36). Fragments of another papyrus, in the Turin Museum, are considered by Lieblein (_Deux Papyras Hieratiques_, Christiania, 1868) also to represent a mine of the time of Rameses I. If so, this one dates from about 1400 B.C. As to an actual map of underground workings (disregarding illustrations) we know of none until after Agricola's time. At his time maps were not made, as will be gathered from the text. [17] For greater clarity we have in a few places interpolated the terms "major" and "minor" triangles. [18] The names of the instruments here described in the original text, their German equivalents in the Glossary, and the terms adopted in translation are given below:-- LATIN TEXT. GLOSSARY. TERMS ADOPTED. _Funiculus_ -- Cord _Pertica_ _Stab_ Rod _Hemicyclium_ _Donlege bretlein_ Hemicycle _Tripus_ _Stul_ Tripod _Instrumentum cui _Compass_ Compass index_ _Orbis_ _Scheube_ Orbis _Libra stativa_ _Auffsafz_ Standing plummet level _Libra pensilis_ _Wage_ Suspended plummet level _Instrumentum cui _Der schiner Swiss compass index Alpinum_ compass_ [19] It is interesting to note that the ratio of any length so obtained, to the whole length of the staff, is practically equal to the cosine of the angle represented by the corresponding gradation on the hemicycle; the gradations on the rod forming a fairly accurate table of cosines. [20] It must be understood that instead of "plotting" a survey on a reduced scale on paper, as modern surveyors do, the whole survey was reproduced in full scale on the "surveyor's field."