But it seems to be less known that adamas also at first denoted steel. This is expressly said by Hesychius, and many epithets derived from adamas are applied to articles made of steel or of iron. Among these may be mentioned the helmet of Hercules, in Hesiod[807], and the so-called adamantine chains, gates, and bars of the poets, which in dictionaries are always explained as consisting of precious stones.
It was not till a late period that this word was applied to the most costly of all the precious stones. In this sense it occurs neither in Homer, Hesiod, Herodotus, Orpheus, nor Dioscorides, though the first of these writers often describes various kinds of valuable ornaments. Goguet and others thence conclude that the diamond was not then known. At present I cannot enter into the history of this stone; but I must own, that I consider the knowledge of it to be older, and suspect that it was first introduced under another name, and is mentioned by Orpheus and some others under that of jasper (jaspis). This poet compares his jaspis to rock crystal, and says that it kindles fire in the same manner. That he knew how to use rock crystal as a burning-glass, he expressly tells us himself; but he certainly could not procure a diamond of such a size as to be able to burn with it. From its vitreous nature however he conjectured, and very properly, that it might be employed for that purpose. He calls the jaspis transparent, compares it to glass, and says that it had that sky colour which at present is named color hyalinus. This is probably the reason why Dioscorides and others call some kinds of jasper transparent and sky-coloured. The jaspis in the Revelation of St. John[808], described as a costly transparent crystalline kind of stone, was perhaps our diamond, which afterwards was everywhere distinguished by that name.
The Romans borrowed from the Greeks the word chalybs; and in consequence of a passage in Pliny[809], many believe that they gave also to steel the name of acies, from which the Italians made their acciajo, and the French their acier. The word acies, however, denoted properly the steeled or cutting part only of an instrument. From this, in later times, was formed aciarium, for the steel which gave the instrument its sharpness, and also aciare to steel[810].
At present there are two methods of making steel; the first of which is by fusion either from iron-stone or raw iron, and the second by cementation. I have never found in the works of the ancients any traces of steel prepared by cementation; nor am I acquainted with the antiquity of that process, though the ancients, without knowing it, employed it for brass. Spielman says[811], that Pliny in one part calls it tostio; but this word occurs neither in Pliny nor in any ancient writer. It is however possible that the word torrere may somewhere signify cementation, but I have not yet met with an instance of it.
The preparation however by fusion, as practised by the Chalybes, has been twice described by Aristotle; but as I have already given in another work[812] everything I was able to collect towards an explanation of these passages, I shall not here repeat it. I shall only remark, that the steel of the ancients, in consequence of not being cemented, suffered itself to be hammered, and was not nearly so brittle as the hardest with which we are acquainted at present.
On the other hand, the singular method of preparing steel employed by the Celtiberians, in Spain, deserves to be here described. According to the account of Diodorus[813] and Plutarch[814], the iron was buried in the earth, and left in that situation till the greater part of it was converted into rust. What remained, without being oxydized, was afterwards forged and made into weapons, and particularly swords, with which they could cut asunder bones, shields, and helmets. However improbable this may appear, it is nevertheless the process still used in Japan; and Swedenborg has introduced it among the different methods of making steel[815].
The art of hardening steel by immersing it suddenly, when red-hot, in cold water, is very old[816]. Homer says, that when Ulysses bored out the eye of Polyphemus with a burning stake, it hissed in the same manner as water when the smith immerses in it a piece of red-hot iron, in order to harden it[817]. Sophocles uses the comparison of being hardened like immersed iron[818]; and Salmasius[819] quotes a work of an old Greek chemist, who treats on the method of hardening iron in India. It is also a very ancient opinion, that the hardening depends chiefly on the nature of the water. Many rivers and wells were therefore in great reputation, so that steel works were often erected near them, though at a considerable distance from the mines. Instances of this may be found in Pliny[820] and in Justin[821]. The more delicate articles of iron were not quenched in water, but in oil.
An opinion, it is well known, long prevailed, that there were various fluids and mixtures which communicate to steel different degrees of hardness, and every artist thought he knew a peculiar hardening kind of water, the preparation of which he kept a secret. This notion is by some still maintained[822]; because there are often found stones cut by the ancients, which the moderns, on account of their hardness, as is believed, have seldom ventured to touch. Of this kind is the hardest porphyry. There are people who still endeavour to find out that hardening kind of water, in which the ancients prepared their tools for cutting such stones. According to Vasari[823], that water was actually discovered by the archduke Cosmo, in the year 1555. Among a large collection of stones he had a block of porphyry, from which he wished a bason to be made for a well, but was told by the most experienced artists that it was impossible. On this, says Vasari, in order to render the work possible, he prepared from certain herbs, which he does not name, a water wherein the red-hot tools were quenched, and by these means so hardened, that they were capable of cutting porphyry. With tools tempered in this manner the artist Francesco del Tadda not only made the required bason, but various other curious articles[824].
Winkelman, therefore, does injustice to Vasari when he says, “Vasari, in pretending that Cosmo archduke of Tuscany discovered a water for making porphyry soft, betrays childish credulity.” On the contrary, he very properly asserts that there is no water of such a quality as to soften porphyry; though Porta and many old writers imagined that they were acquainted with one capable of producing on that stone, which they considered as a species of marble, the same effects as an acid does on the latter. But Vasari says nothing of the kind.
After Tadda’s death, the art of cutting porphyry came to Raphael Curradi, who communicated to Dominico Corsi this secret, which was afterwards employed by Cosimo Silvestrini[825]. I, however, agree in opinion with Winkelman and Fiorillo, our learned connoisseur in the arts, that the method of working porphyry was known in every age, even in the most barbarous, though artists, no doubt, preferred working on other stones which were less brittle and hard. We know however from the latest researches, that all the kinds of hardening water hitherto invented are in nothing superior to common water; and that in hardening more depends on the nature of the steel, or rather on the degree of heat, than on the water; although it is true that the workman does right when he adds to the water a thin cake of grease, or pours over it hot oil, through which the steel must necessarily pass before it enters the water, for by these means it is prevented from acquiring cracks and flaws.