For my part, I find in this passage as few traces of smalt as M. Gmelin; and I agree with him in opinion that the strong and unpleasant mixtures arising from cobalt would, had it been known, have induced the ancients to make particular mention of it in their writings. Would not the arsenic, which is so often combined with cobalt, have given occasion to many reports respecting the dangerous properties of these minerals? And would not arsenic and bismuth have been sooner known, had preparations of cobalt been made at so early a period? It is a circumstance of great weight also, that in the places where the ancients had mines, and where antiquities painted or tinged blue, and resembling in colour that produced by cobalt, have been dug up, cobalt has not been discovered, or has been discovered only in modern times. At present we know nothing of Egyptian, Arabian, Ethiopian, Italian, and Cyprian cobalt; and in Spain[1477] this mineral was first found in the reign of Philip IV. I shall here observe, that the island of Cyprus was formerly so abundant in copper, that, in a mineralogical sense, it might be called the island of Venus; and we can therefore entertain the less doubt that the cæruleum Cyprium was copper-blue.
The principal reason, however, why Lehmann, Pauw[1478], Ferber, Delaval, and others, think that the ancients used smalt, and were acquainted with cobalt, is that, as has been already said, various antiquities both of painting and enamel have been discovered, in which a blue appears that seems to give grounds for conjecturing that it was produced by cobalt. Ferber[1479] speaks of blue glass squares in mosaic-work; and Delaval mentions old Egyptian glass-work of this colour[1480]. It is well known also that the Chinese and people of Japan gave to their porcelain that fine blue colour, for which it is celebrated, long before the discovery of smalt in Europe. On mummies a blue is seen likewise, which, even after so many centuries, seems to have lost little or nothing of its beauty[1481]. We must therefore allow that the ancients used either ultramarine or cobalt.
The first opinion seems, in regard of porcelain, to be confirmed by Duhalde[1482], who speaks of a mine of azur, and relates that the Chinese, in modern times, use instead of it, for painting their porcelain, a blue colour brought from foreign countries. It is probable that by the former he means lapis lazuli, and by the latter smalt, which is sent in large quantities from Europe to China. The invention of ultramarine, however, appears to me too new, its effect on porcelain too uncertain, and its price too high to allow us to suppose that it has been much used. We should therefore have been almost obliged to adopt the latter opinion, had not M. Gmelin proved by chemical experiments[1483] that it is not only possible to give to glass and enamel a blue colour by means of iron, but that the before-mentioned antiquities, upon which so much stress has been laid, show not the smallest traces of cobalt. He even made experiments upon blue tiles, found in a Roman tessellated foot-pavement at Montbeillard; and likewise on the blue paint of the mummy which was presented to our university by the king of Denmark[1484]. He has also mentioned various articles on which a blue colour is produced by the vitrification of iron. Of this nature are in particular those slags found near the smelting-houses at the iron-mines of the Harz forest; and I myself have seen slags which were of a blue colour exceedingly beautiful. Volcanic slags, or scoriæ, found in the neighbourhood of Verona, Vicenza, and other parts of Italy, are mentioned also by Ferber[1485], which seems to confirm the conjecture of Dr. Bruckmann[1486], that the ancients may have used such slags for their works. It is probable that the ancients were first induced by the blue slag of their smelting-houses to make experiments on the colouring of glass with iron, and that in this art they acquired a dexterity not possessed at present, because it was abandoned by our ancestors after the invention of smalt, which is much more beautiful; and which can be used more easily and with more certainty. I cannot, however, deny that I have often lamented this loss when I saw the excellent blue in the painted windows at Gouda, Goslar, and other places; though its beauty is much heightened by the transparency of the glass, and the strong light that falls upon it from without.
I shall now proceed to the invention of the colour prepared from cobalt. About the end of the fifteenth century, cobalt appears to have been dug up in great quantity in the mines on the borders of Saxony and Bohemia, discovered not long before that period. As it was not known at first to what purpose it could be applied, it was thrown aside as a useless mineral. The miners had an aversion to it, not only because it gave them much fruitless labour, but because it often proved prejudicial to their health by the arsenical particles with which it was combined; and it appears even that the mineralogical name cobalt then first took its rise. At any rate, I have never met with it before the beginning of the sixteenth century; and Mathesius and Agricola seem to have first used it in their writings. Frisch derives it from the Bohemian word kow, which signifies metal; but the conjecture that it was formed from cobalus, which was the name of a spirit that, according to the superstitious notions of the times, haunted mines, destroyed the labours of the miners, and often gave them a great deal of unnecessary trouble, is more probable; and there is reason to think that the latter is borrowed from the Greek. The miners, perhaps, gave this name to the mineral out of joke, because it thwarted them as much as the supposed spirit, by exciting false hopes and rendering their labour often fruitless[1487]. It was once customary, therefore, to introduce into the church service a prayer that God would preserve miners and their works from kobolts and spirits.
Respecting the invention of making a useful kind of blue glass from cobalt, we have no better information than that which Klotzsch[1488] has published from the papers of Christian Lehmann. The former, author of an historical work respecting the upper district of the mines in Misnia, and a clergyman at Scheibenberg, collected with great diligence every information in regard to the history of the neighbouring country, and died, at a great age, in 1688. According to his account, the colour-mills, at the time when he wrote, were about a hundred years old; and as he began first to write towards the end of the thirty years’ war, the invention seems to fall about 1540 or 1560. He relates the circumstance as follows: “Christopher Schurer, a glass-maker at Platten, a place which belongs still to Bohemia, retired to Neudeck, where he established his business. Being once at Schneeberg, he collected some of the beautiful coloured pieces of cobalt which were found there, tried them in his furnace; and finding that they melted, he mixed some cobalt with the vitreous mass, and obtained fine blue glass. At first he prepared it only for the use of the potters; but in the course of time it was carried as an article of merchandize to Nuremberg, and thence to Holland. As painting on glass was then much cultivated in the latter, the artists there knew better how to appreciate this invention. Some Dutchmen therefore repaired to Neudeck, in order that they might learn the process used in preparing this new colour. By great promises they persuaded the inventor to remove to Magdeburg, where he also made glass from the cobalt of Schneeberg; but he again returned to his former residence, where he constructed a hand-mill to grind his glass, and afterwards erected one driven by water. At that period the colour was worth seven dollars and a half per cwt., and in Holland from fifty to sixty florins. Eight colour-mills of the same kind, for which roasted cobalt was procured in casks from Schneeberg, were soon constructed in Holland; and it appears that the Dutch must have been much better acquainted with the art of preparing, and particularly with that of grinding it, than the Saxons; for the elector John George sent for two colour-makers from Holland, and gave a thousand florins towards enabling them to improve the art. He was induced to make this advance chiefly by a remark of the people of Schneeberg, that the part of the cobalt which dropped down while it was roasting contained more colour than the roasted cobalt itself. In a little time other colour-mills were erected around Schneeberg. Hans Burghard, a merchant and chamberlain of Schneeberg, built one by which the eleven mills at Platten were much injured. Paul Nordhoff, a Frieslander, a man of great ingenuity, who lived at the Zwitter-mill, made a great many experiments in order to improve the colour, by which he was reduced to so much poverty that he was at length forced to abandon that place, where he had been employed for ten years in the colour-manufactory. He retired to Annaberg, established there in 1649, by the assistance of a merchant at Leipsic, a colour-manufactory, of which he was appointed the director; and by these means rendered the Annaberg cobalt of utility. The consumption of this article however must have decreased in the course of time; for in the year 1659, when there were mills of the same kind at more of the towns in the neighbourhood of mines, he had on hand above 8000 quintals.” Thus far Lehmann.
This information is in some measure confirmed by Melzer[1489], who says that the mines of Schneeberg, which were first discovered in the middle of the fifteenth century, had declined so much towards the middle of the sixteenth, that it was impossible to get any profit by them till the year 1550, when a greater advantage arose from the new method of using cobalt. About this period a contract was entered into with the Dutch, who agreed to take the roasted cobalt at a certain price. Lehmann[1490] says, but without adducing any proofs, that a manufactory for making blue glass was erected by Sebastian Preussler, between Platten and Eybenstock, so early as 1571. Rossler[1491], who died in 1673, in the seventy-sixth year of his age, gives us to understand that a century and a half before his time, cobalt was procured and sold as zaffer; but that the colour-mills in the country had been established only about sixty years. I conjecture therefore that the roasted cobalt, to which sand was added, in order that the nature of it might be better concealed, and the further preparation of it rendered more difficult, was given up to the Dutch, even so early as the beginning of the sixteenth century[1492], and that these people by melting it anew, or at any rate by pounding it finer, derived the greatest benefit from it long before the Saxons themselves constructed mills according to the model of those used in Holland. At present many Dutchmen grind German cobalt with very great advantage[1493].
It appears that this new colour was not made known in books till a late period. Agricola was not acquainted with the blue glass, nor is zaffera mentioned either by him or Mathesius. Albin also, who indeed derived the greater part of his information from these two writers, says not a word respecting it; but he tells us that bismuth when put in vessels grew together again[1494]. He seems therefore to allude to cobalt roasted and mixed with sand, which when packed up becomes a solid body, whereas bismuth which has been purified by roasting can never assume that state. Vanuccio Biringoccio, the oldest writer in whose works I have as yet observed the name zaffera, describes its use for painting glass, and calls it a heavy mineral, without defining it any further. Cardan[1495] gives the name of zaffera to an earth which colours glass blue. Cæsalpin says it is a stone[1496]; and Julius Scaliger must have known as little of it, else he would have mentioned it in his Exercitations on Cardan. Porta, who employed great diligence to acquire knowledge of this kind, often mentions zaphara figlinorum, without telling us what it is; but he describes how it must be melted, poured into water, pounded, sifted, and reduced into a fine powder in order to be employed for making artificial precious stones[1497]. Neri, who wrote about the year 1609[1498], knew nothing more of it; and Merret, the commentator on Neri, who lived in the middle of the sixteenth century[1499], confesses that he knew not what zaffera was, but he believed that it was a new German invention, at least that it was brought from Germany, and that it seemed to him to be made from copper and sand, with the addition perhaps of calamine. The first person who properly explained zaffera in his writings, and gave a correct account of the method of preparing it, is, in my opinion, Kunkel[1500] in his annotations on Neri and Merret. That writer says, zaffera was by the miners called zafloer, and that sand was mixed with it only that the powder-blue used by women for linen, and by painters called blue smalt, might not be imitated in other countries.
Rosler says the Bohemian cobalt is not so good as that of Misnia, and that its colour is more like that of ashes. That Brandt, a member of the Council of Mines in Sweden, first asserted that cobalt contained a peculiar kind of metal, must be so well known to mineralogists, that it scarcely deserves to be mentioned[1501].
FOOTNOTES
[1472] See what is said under the article [Artificial Rubies].