De Re Metallica Part 40

Quicksilver reduced from ore by distillation Prior to Christian Era

Silver parted from gold by cementation with salt Prior to " "

Bra.s.s made by cementation of copper and calamine Prior to " "

Zinc oxides obtained from furnace fumes by Prior to " "

construction of dust chambers

Antimony reduced from ores by smelting (accidental) Prior to " "

Gold recovered by amalgamation Prior to " "

Refining of copper by repeated fusion Prior to " "

Sulphide ores smelted for copper Prior to " "

Vitriol (blue and green) made Prior to " "

Alum made Prior to " "

Copper refined by oxidation and poling Prior to 1200 A.D.

Gold parted from copper by cupelling with lead Prior to 1200 A.D.

Gold parted from silver by fusion with sulphur Prior to 1200 A.D.

Manufacture of nitric acid and _aqua regia_ Prior to 1400 A.D.

Gold parted from silver by nitric acid Prior to 1400 A.D.

Gold parted from silver with antimony sulphide Prior to 1500 A.D.

Gold parted from copper with sulphur Prior to 1500 A.D.

Silver parted from iron with antimony sulphide Prior to 1500 A.D.

First text book on a.s.saying Prior to 1500 A.D.

Silver recovered from ores by amalgamation Prior to 1500 A.D.

Separation of silver from copper by liquation Prior to 1540 A.D.

Cobalt and manganese used for pigments Prior to 1540 A.D.

Roasting copper ores prior to smelting Prior to 1550 A.D.

Stamp-mill used Prior to 1550 A.D.

Bis.m.u.th reduced from ore Prior to 1550 A.D.

Zinc reduced from ore (accidental) Prior to 1550 A.D.

Further, we believe it desirable to sketch at the outset the development of metallurgical appliances as a whole, leaving the details to special footnotes; otherwise a comprehensive view of the development of such devices is difficult to grasp.

We can outline the character of metallurgical appliances at various periods in a few words. It is possible to set up a description of the imaginary beginning of the "bronze age" prior to recorded civilization, starting with the savage who accidentally built a fire on top of some easily reducible ore, and discovered metal in the ashes, etc.; but as this method has been pursued times out of number to no particular purpose, we will confine ourselves to a summary of such facts as we can a.s.semble. "Founders' h.o.a.rds" of the bronze age are scattered over Western Europe, and indicate that smelting was done in shallow pits with charcoal. With the Egyptians we find occasional inscriptions showing small furnaces with forced draught, in early cases with a blow-pipe, but later--about 1500 B.C.--with bellows also. The crucible was apparently used by the Egyptians in secondary melting, such remains at Mt. Sinai probably dating before 2000 B.C. With the advent of the Prophets, and the first Greek literature--9th to 7th century B.C.--we find frequent references to bellows. The remains of smelting appliances at Mt. Laurion (500-300 B.C.) do not indicate much advance over the primitive hearth; however, at this locality we do find evidence of the ability to separate minerals by specific gravity, by washing crushed ore over inclined surfaces with a sort of buddle attachment. Stone grinding-mills were used to crush ore from the earliest times of Mt. Laurion down to the Middle Ages. About the beginning of the Christian era the writings of Diodorus, Strabo, Dioscorides, and Pliny indicate considerable advance in appliances. Strabo describes high stacks to carry off lead fumes; Dioscorides explains a furnace with a dust-chamber to catch _pompholyx_ (zinc oxide); Pliny refers to the upper and lower crucibles (a forehearth) and to the pillars and arches of the furnaces. From all of their descriptions we may conclude that the furnaces had then reached some size, and were, of course, equipped with bellows. At this time sulphide copper and lead ores were smelted; but as to fluxes, except lead for silver, and lead and soda for gold, we have practically no mention. Charcoal was the universal fuel for smelting down to the 18th century. Both Dioscorides and Pliny describe a distillation apparatus used to recover quicksilver. A formidable list of mineral products and metal alloys in use, indicate in themselves considerable apparatus, of the details of which we have no indication; in the main these products were lead sulphide, sulphate, and oxide (red-lead and litharge); zinc oxide; iron sulphide, oxide and sulphate; a.r.s.enic and antimony sulphides; mercury sulphide, sulphur, bitumen, soda, alum and potash; and of the alloys, bronze, bra.s.s, pewter, electrum and steel.

From this period to the period of the awakening of learning our only light is an occasional gleam from Theophilus and the Alchemists. The former gave a more detailed description of metallurgical appliances than had been done before, but there is little vital change apparent from the apparatus of Roman times. The Alchemists gave a great stimulus to industrial chemistry in the discovery of the mineral acids, and described distillation apparatus of approximately modern form.

The next period--the Renaissance--is one in which our descriptions are for the first time satisfactory, and a discussion would be but a review of _De Re Metallica_.

[2] See footnote 2, p. 267, on verbs used for roasting.

[3] Agricola has here either forgotten to take into account his three-palm-thick furnace walls, which will make the length of this long wall sixty-one feet, or else he has included this foot and a half in each case in the six-foot distance between the furnaces, so that the actual clear s.p.a.ce is only four and a half feet between the furnace with four feet on the ends.

[4] The paucity of terms in Latin for describing structural members, and the consequent repet.i.tion of "beam" (_trabs_), "timber" (_tignum_), "billet" (_tigillum_), "pole" (_a.s.ser_), with such modifications as small, large, and transverse, and with long explanatory clauses showing their location, renders the original very difficult to follow. We have, therefore, introduced such terms as "posts," "tie-beams," "sweeps,"

"levers," "rafters," "sills," "moulding," "braces," "cleats,"

"supports," etc., as the context demands.

[5] This set of rafters appears to start from the longitudinal beam.

[6] Devices for creating an air current must be of very old invention, for it is impossible to conceive of anything but the crudest melting of a few simple ores without some forced draft. Wilkinson (The Ancient Egyptians, II, p. 316) gives a copy of an ill.u.s.tration of a foot-bellows from a tomb of the time of Thotmes III. (1500 B.C.). The rest of the world therefore, probably obtained them from the Egyptians. They are mentioned frequently in the Bible, the most pointed reference to metallurgical purposes being Jeremiah (VI, 29): "The bellows are burned, the lead is consumed in the fire; the founder melteth in vain; for the wicked are not plucked away." Strabo (VII, 3) states that Ephorus ascribed the invention of bellows to Anacharsis--a Thracian prince of about 600 B.C.

[7] This whole arrangement could be summarized by the word "hinge."

[8] The rim of this wheel is obviously made of segments fixed in two layers; the "disc" meaning the aggregate of segments on either side of the wheel.

[9] It has not been considered necessary to introduce the modern term _twyer_ in these descriptions, as the literal rendering is sufficiently clear.

[10] _Ferruminata_. These accretions are practically always near the hearth, and would correspond to English "sows," and therefore that term has been adopted. It will be noted that, like most modern metallurgists, Agricola offers no method for treating them. Pliny (x.x.xIV, 37) describes a "sow," and uses the verb _ferruminare_ (to weld or solder): "Some say that in the furnace there are certain ma.s.ses of stone which become soldered together, and that the copper fuses around it, the ma.s.s not becoming liquid unless it is transferred to another furnace; it thus forms a sort of knot, as it were, of the metal."

[11] What are known in English as "crucible," "furnace well,"

"forehearth," "dipping-pot," "tapping-pot," "receiving-pot," etc., are in the text all _catinus_, _i.e._, crucible. For easier reading, however, we have a.s.signed the names indicated in the context.

[12] _Panes ex pyrite conflati_. While the term _matte_ would cover most cases where this expression appears, and in many cases would be more expressive to the modern reader, yet there are instances where the expression as it stands indicates its particular origin, and it has been, therefore, considered advisable to adhere to the literal rendering.

[13] _Molybdaena_. See note 37, p. 476. It was the saturated furnace bottoms from cupellation.

[14] The four elements were earth, air, fire, and water.

[15] "Stones which easily melt in the fire." Nowhere in _De Re Metallica_ does the author explain these substances. However in the _Interpretatio_ (p. 465) he gives three genera or orders with their German equivalents, as follows:--"_Lapides qui igni liquesc.u.n.t primi generis,--Schone flusse; secundi,--flusse zum schmeltzen flock quertze; tertii,--quertze oder kiselstein."_ We confess our inability to make certain of most of the substances comprised in the first and second orders. We consider they were in part fluor-spar, and in any event the third order embraced varieties of quartz, flint, and silicious material generally. As the matter is of importance from a metallurgical point of view, we reproduce at some length Agricola's own statements on the subject from _Bermannus_ and _De Natura Fossilium_. In the latter (p.

268) he states: "Finally there now remain those stones which I call 'stones which easily melt in the fire,' because when thrown into hot furnaces they flow (_fluunt_). There are three orders (_genera_) of these. The first resembles the transparent gems; the second is not similar, and is generally not translucent; it is translucent in some part, and in rare instances altogether translucent. The first is sparingly found in silver and other mines; the second abounds in veins of its own. The third genus is the material from which gla.s.s is made, although it can also be made out of the other two. The stones of the first order are not only transparent, but are also resplendent, and have the colours of gems, for some resemble crystal, others emerald, heliotrope, lapis lazuli, amethyst, sapphire, ruby, _chrysolithus_, _morion_ (cairngorm?), and other gems, but they differ from them in hardness.... To the first genus belongs the _lapis alabandicus_ (modern albandite?), if indeed it was different from the alabandic carbuncle. It can be melted, according to Pliny, in the fire, and fused for the preparation of gla.s.s. It is black, but verging upon purple. It comes from Caria, near Alabanda, and from Miletus in the same province. The second order of stones does not show a great variety of colours, and seldom beautiful ones, for it is generally white, whitish, greyish, or yellowish. Because these (stones) very readily melt in the fire, they are added to the ores from which the metals are smelted. The small stones found in veins, veinlets, and the s.p.a.ces between the veins, of the highest peaks of the Sudetic range (_Suditorum montium_), belong partly to this genus and partly to the first. They differ in size, being large and small; and in shape, some being round or angular or pointed; in colour they are black or ash-grey, or yellow, or purple, or violet, or iron colour. All of these are lacking in metals. Neither do the little stones contain any metals which are usually found in the streams where gold dust is collected by washing.... In the rivers where are collected the small stones from which tin is smelted, there are three genera of small stones to be found, all somewhat rounded and of very light weight, and devoid of all metals. The largest are black, both on the outside and inside, smooth and brilliant like a mirror; the medium-sized are either bluish black or ash-grey; the smallest are of a yellowish colour, somewhat like a silkworm. But because both the former and the latter stones are devoid of metals, and fly to pieces under the blows of the hammer, we cla.s.sify them as sand or gravel. Gla.s.s is made from the stones of the third order, and particularly from sand. For when this is thrown into the heated furnace it is melted by the fire.... This kind of stone is either found in its own veins, which are occasionally very wide, or else scattered through the mines. It is less hard than flint, on account of which no fire can be struck from it. It is not transparent, but it is of many colours--that is to say, white, yellowish, ash-grey, brown, black, green, blue, reddish or red. This genus of stones occurs here and there in mountainous regions, on banks of rivers, and in the fields. Those which are black right through to the interior, and not merely on the surface, are more rare; and very frequently one coloured vein is intersected by another of a different colour--for instance, a white one by a red one; the green is often spotted with white, the ash-grey with black, the white with crimson.

Fragments of these stones are frequently found on the surface of the earth, and in the running water they become polished by rubbing against stones of their own or of another genus. In this way, likewise, fragments of rocks are not infrequently shaped into spherical forms....

This stone is put to many uses; the streets are paved with it, whatever its colour; the blue variety is added to the ash of pines for making those other ashes which are used by wool-dyers. The white variety is burned, ground, and sifted, and from this they make the sand out of which gla.s.s is made. The whiter the sand is, the more useful it is."

Perusal of the following from _Bermannus_ (p. 458) can leave little doubt as to the first or second order being in part fluor-spar. Agricola derived the name _fluores_ from _fluo_ "to flow," and we in turn obtain "fluorite," or "fluorspar," from Agricola. "_Bermannus_.--These stones are similar to gems, but less hard. Allow me to explain word for word.

Our miners call them _fluores_, not inappropriately to my mind, for by the heat of fire, like ice in the sun, they liquefy and flow away. They are of varied and bright colours. _Naevius_.--Theophrastus says of them that they are made by a conflux in the earth. These red _fluores_, to employ the words just used by you, are the ruby silver which you showed us before. _Bermannus_.--At the first glance it appears so, although it is not infrequently translucent. _Naevius_.--Then they are rubies?

_Bermannus_.--Not that either. _Naevius_.--In what way, then, can they be distinguished from rubies? _Bermannus_.--Chiefly by this sign, that they glitter more feebly when translucent. Those which are not translucent may be distinguished from rubies. Moreover, _fluores_ of all kinds melt when they are subject to the first fire; rubies do not melt in fire. _Naevius_.--You distinguish well. _Bermannus_.--You see the other kind, of a paler purple colour? _Naevius_.--They appear to be an inferior kind of amethyst, such as are found in many places in Bohemia.

_Bermannus_.--Indeed, they are not very dissimilar, therefore the common people who do not know amethysts well, set them in rings for gems, and they are easily sold. The third kind, as you see here, is white.