66 



NATURE 



[Nov. 1 8, i8So 



past thirty years, and remembering that the success with which 

 any manufacturing art is practised must bear a direct relation to 

 the way in which it is taught, we cannot but feel how greatly 

 this development of metallurgical knowledge must have been 

 influenced by Dr. Percy's labours. During this period the con- 

 ditions under which metallurgy is practised have changed con- 

 siderably; for the field of knowledge has so widely extended, 

 the scale on which operations are conducted is now so great, and 

 the mechanical appliances they involve are so varied and com- 

 plicated, that while the interest of our subject is deepened its 

 difficulty is gravely increased. 



In turning to the history of metallurgy, more especially in its 

 relation to chemical science, it is easy to be led away by the 

 charm of the antiquarian riches of our subject into devoting too 

 much time to this kind of literary research ; I may remind you 

 however that much of what is bath interesting and full of 

 suggestion, even at the present day, is to be found buried in 

 the treatises by the old writers whose work we inherit and 

 continue. 



Primitive met.-illurgical processes are referred to in some of 

 the oldest known historical records ; naturally therefore the 

 development of metallurgy as a science must have been long 

 preceded by its practice as an art, an art for which a place has 

 even been claimed among the religious systems of antiquity.' 

 The earlier literature of the subject consists mainly of descriptions 

 of processes ; but it is well known that chemistry was to a great 

 extent built up on a metallurgic basis, and Black's singularly 

 advanced definition of chemistry as the "effects produced by 

 heat and mixture " - might w ell be applied to metallurgy. But 

 of all the phenomena of our subject, probably none have more 

 contributed to advance the science of chemistry than those bear- 

 ing upon the relations between oxygen and lead ; indeed the 

 interest attaching to the mutual behaviour of these two elements 

 is so great that I propose devoting a few minutes to i s consider- 

 ation, more especially as I am anxious to indicate the influence 

 of an ancient process on the scientific views of the present day. 



When lead is melted with free access of air, a readily fusible 

 substance forms on its surface. This substance may be allowed 

 to flow away, or if the metal is contained in a suitable porous 

 receptacle, the fusible oxide sinks into this containing vessel ; in 

 either case the oxidation of the lead affords a means of separat- 

 ing it from precious or inoxidisable metals if any were originally 

 present in the lead. The above fact has been known from remote 

 antiquity, and the early Jewish writers allude to it as old and 

 well known. They clearly show, for instance, that lead can be 

 removed from silver by being "consumed of the fire," while the 

 silver is not affected. That the Greeks knew and practised the 

 method is abundantly proved, if only by certain specimens of 

 gold and silver now in the adjoining museum, which were recently 

 discovered by Dr. Schliemann. The Arabians investigated the 

 subject ; for passing to Geber,' the greatest of the early chemists 

 (he died in 777)> we find a remark.able account of cupellation ; 

 he also describes the conver>ion of lead into a fine powder by 

 calcination with much clearness, and he noticed the fact that 

 after calcination the mass has "acquired a new weight in the 

 operation." I think his subsequent observations on the reduc- 

 tion of altered metals from their "calxes" show that he knew 

 the weight to be increased ; in any case it is interesting to re- 

 member that his work was in a sense quantitative. He more- 

 over was cognisant of the fact that two different substances may 

 be produced by heating lead in air, and he assumed that " in the 

 fire of calcination a fugitive and inflammable substance is 

 abolished." The alchemists refer continually to the subject, and 

 " deliver themselves," as Roger Bacon said, in his "Speculum 

 Alchimoe," " in the enigmas and riddles w ith which they clouded 

 and left shadowed to us the most noble science." In the middle 

 of the sixteenth century the truly accomplisied metallurgist 

 Biringuccio,' contemporary of Paracelsus and Agricola, seems to 

 have been specially attracted by the phenomenon in question, 

 and he remarks : " If we had not lead we should work in vain 

 for the precious metals, for without its aid we could not extract 

 gold or silver from the stones containing them. . . . The 

 alchemists also," he s.aid, "make use of it in their operations, 

 calcining it by itself or with other lubstances ; but," he goes on 

 to observe, " the calcination, conducted in a reverberatory fur- 



' Rossignol, " Les Mciaux d.^ns I'Antiquit^ " (1S63). 



" " Lectures by Joseph Black, M.D.," vol. i, p. 8 (Edin., 1803). 



3 " The VVorlcs of Geber," transhted by R. Russell (1686), pp. 74, 7S, 



•• " Pirotechnia " (\'inegia, 1S40). translat 

 Rouen, 1627), p. 41. 



I'D French by T, Vincent 



nace, is accompanied by a marvellous effect, (he result of which 

 should not be passed by in silence ; for lead thus treated increases 

 10 per cent, in weight, and, considering that most things are 

 consumed in the fire, it is remarkable that the weight of lead is 

 increased, and not diminished." Although he subsequently gives 

 evidence of much accurate knowledge of practical metallurgy, his 

 views as to this particular phenomenon were hardly in advance of 

 Geber's ; but we may claim Biringuccio as an early metallurgist, 

 who knew the facts, and recognised that they were theoretically 

 important. It was not until nearly a century later (1630) that a 

 French chemist, Jean Key,' stated that the increase in weight 

 came from the air. The problem attracted much attention in 

 England, and it is not a little interesting that among the very 

 first experiments recorded by our own Royal Society is a metal- 

 lurgical series relating to the weight of lead increased in the fire on 

 the " copeU " at the assay office in the Tower, the account being 

 brought in by Lord Brouncker in February, 1661." [Subse- 

 quently, in 1669, John Mayo shovved that the increase in weight 

 of calcined metals was due to a "spiritus" from the air.' Boyle 

 heated lead in a small retort,'' and attributed the increase in 

 weight, as Lemery also did,'' to his having "arrested and 

 weighed igneous corpuscles." ^ 



I need hardly point out how important this calcination of lead 

 was considered by those who defended the Phlogistic theory in 

 regard to chemical change, a theory which, for more than a 

 century, exerted so profound an influence on scientific thought. 

 [.Vs this theory originated w ith a metallurgist, Becker, it was 

 considered at some length, and it was made evident that the 

 main aim of chemical investigation down to the end of hast 

 century was the explanation of calcination, combustion, or 

 oxidation, and that lead was especially usefid in solving the 

 problem. J 



I might perhaps add that the absorption of oxygen by molten 

 litharge has furnished M. Ste. Claire- Deville,' a physicist and 

 metallurgist, with an important step in the argument as to disso- 

 ciation, and thus connects the history of the metal with the 

 great adv.!nce on the borderland of chemistry and physics in 

 modern times, to which I shall constantly refer. 



The above remarks will, I tnist, be sufficient to show that 

 conclusions of the utmost importance in the history of chemical 

 theory were based on a very ancient metallurgical process ; but I 

 have also selected lead as an illustration, because, in the gradual 

 development of the knowledge derived in the first instance from 

 its metallurgy, there is much that is typical of the mutual relation 

 of theory and practice that still prevails. 



When Dr. Percy began his teaching, he considered at some 

 length the kind of assistance that other sciences might be 

 expected to render cur subject, considered as a manufacturing 

 art ; and this at the time was necessary for two reasons : ' first, 

 because he was "able to adduce from his own observation 

 several striking ca^es in illustration of the advantage of the 

 application of science to practical metallurgy ; and, second, 

 because the practice of metallurgy, so far as relates to magnitude 

 of operation, having been developed to an unparalleled extent 

 in this country in the absence of specific public instruction on 

 the subject, it was necessary to justify the providing of such 

 insiruction." 



The absence of accurate knowledge en the part of those 

 engaged in metallurgy was lamented as long ago as 1700, in 

 an "Inaugural Dissertation of Pyrotechnical Metallurgy," de- 

 livered, on March 25 of that year, in the University of Magde- 

 burg ; no less a person than the great supporter of the theory of 

 Phlogiston, George Ernest Stahl, presided, and the lecturer v 



I " Essays de Jean Rey " (reprinted in Paris, 1777), p. 64. 



^ MS. Register book of the Royal Society. 



: ■■ Tractatus quinque Medico-Physici," p. 25 cl Sty. (Oxonii, 167 4>. 



•< Collected works, vcl. iii, (1744), P- 347- 



5 "Cours de Chymie" (1675), 2nd English edition (i686), p. 107. 



6 I am indebted to my friend Prof. Ferguson, M.A., of the University of 

 Glasgow, whose eminence as a historian of chemistry is well known, for 

 'several interesting additional facts in connection with the calcination of 

 metals. After referring to Eck (1489), Glauber (1651). and others, he writes : 

 •■One of the most curious passages 1 know is in the ' Hippocrates Chemicus 

 of Otto Tachen, or Tachenius, a German who lived at Venice and published 

 his hook there in 1666. He describes how lead, when burnt to minium, 

 increases in weight. This increase he ascribes to a substance of acid cha- 

 racter in the wood used for burning, and then, by a very curious course of 

 argument, based on the sapcnifying powers of litharge, makes out that lead 

 is of the nalure of or contains an alkali, which combines with the * occult 

 acid of the fat." This is a curious anticipation of a verv modern classifica- 

 tion which brings lead into relationship with the alkalies and alkaline earths, 

 as well as of Chevreul's investigations." 



7 " Lecons sur la Dissociation," 1864. 



s Records of the School of Mines, vol. i. pt- i (1851)1 P- 128. 



