404 



NATURE 



[August 27, 1S91 



with which he is familiar. It may all seem simple enough, but 

 the modern process of copper-smelting has been laboriously 

 built up, and has a long and interesting pedigree which may be 

 traced to at least the eighth century, when Geber described the 

 regulus, " coarse metal," as being " black mixed with livid," and 

 our familiar "blue metal" as being "of a most clean and plea- 

 sant violet colour," and indicated the reason for the difference.^ 



(3) The foregoing instances have been given to indicate the 

 general nature of metallurgical chemistry. It will be well now 

 to show how the great advances in metallurgical practice have 

 been made in the past, with a view to ascertain what principles 

 should guide us in the future. 



It is a grave mistake to suppose that in industry, any more 

 than in art, national advance takes place always under the 

 guidance of a master possessed of some new gift of invention ; 

 yet we have been reminded that we are apt to be reverent to 

 these alone, as if the nation had been unprogressive and sud- 

 denly awakened by the genius of one man. The way for any 

 great technical advance is prepared by the patient acquisition of 

 facts by investigators of pure science. Whether the investi- 

 gators are few or many, and consequently whether progress is 

 slow or rapid, will depend in no small measure on the spirit of 

 the nation as a whole. A genius whose practical order of mind 

 enables him to make some great invention suddenly arises, 

 apparently by chance, but his coming will, in most cases, be 

 found to have "followed hard upon" the discovery by some 

 scientific worker of an important fact, or even the accurate 

 determination of a set of physical constants. No elaborate 

 monograph need have reached the practical man — a newspaper 

 paragraph, or a lecture at a Mechanics' Institute may have been 

 sufficient to give him the necessary impulse ; but the possessors 

 of minds which .are essentially practical often forget how valu- 

 able to them have been the fragments of knowledge they have 

 so insensibly acquired that they are almost unconscious of 

 having received any external aid. 



The investigating and the industrial faculty are sometimes, 

 though rarely, united in one individual. Rapid advance is 

 often made by those who are untrammelled by a burden of 

 precedent, but it should be remembered that though the few 

 successes, which have been attained in the course of ignorant 

 practice, may come into prominence, none of the countless 

 failures are seen. 



I would briefly direct attention to certain processes which have 

 been adopted since the year 1849, when Ur. Percy presided over 

 this Section at Birmingham, a great metallurgical centre. In 

 that year the President of the Association made a reference to 

 metallurgy, a very brief one, for Dr. Robinson only said "the 

 manufacture of iron has been augmented six-fold by the use of 

 the puddling-furnace and the hot-blast, both gifts of theory"; 

 and so, it may be added, are most of the important processes 

 which have since been devised. Take the greatest metallurgical 

 advance of all, the Bessemer process, which has probably done 

 more than any other to promote the material advance of all 

 countries. It was first communicated to the world at the 

 Cheltenham Meeting of the British Association, 1856. Its 

 nature is well known, and I need only say that it depends on 

 the fact that when air is blown through a bath of impure molten 

 iron, sufficient heat is evolved by the rapid combustion of 

 silicon, manganese, and carbon, to maintain the bath fluid after 

 these elements have been eliminated, there being no external 

 source of heat, as there is in the puddling furnace or the refinery 

 hearth. We have recently been told that, at an early and 

 perilous stage of the Bessemer process, confidence in the experi- 

 ments was restored by the observation that the temperature of 

 the "blown" metal contained in a crucible was higher than 

 that of the furnace in which it was placed. The historian of the 

 future will not fail to record that the way for the Bessemer 



' It must not be supposed that when commercially pure copper lies on the 

 furnace bed, ready to be transferred to n>ouIds, that ils turbulent career of 

 reactions is over. It might be thought that the few tenths per cent, of im- 

 purity, dissolved oxide, and occluded gas, are so far attenuated by distribu- 

 tion that their interactions must be insignificant. This is far from being the 

 case. I believe the bath of metal is seething from its reactions until the 

 copper is solid, and then polymerizati m proceeds. There may not be a 

 sharply-defined, critical range of temperature within which the metal can 

 alone be successfully worked, and which vanes, as regards its starting-point, 

 with the kind of impurity present, as is the case w.th steel ; but evidence of , 

 molecular change in the solid metal i>i afforded by the pyrometric curves of 

 cooling referred to on p. 405, and by the s ngular behaviour as regards elec- 

 trical resistance, of various samples of copper, in which chemical analysis 

 hardly reveals a difference. 



process had been prepared by the theoretical work of Andrews, 

 1848, and of Favre and Silbermann, 1852, whose work on the 

 calorific power of various elements showed that silicon and phos- 

 phorus might be utilized as fuel, because great heal is engendered 

 by their combustion. 



The basic process for removing phosphorus, a process of great 

 national importance, the development of which we owe to 

 Thomas and Gilchrist, is entirely the outcome of purely theo- 

 retical teaching, in connection with which the names of Griiner 

 and Percy deserve special mention. In the other great group 

 of processes for the production of steel, those in which Siemens's 

 regenerative furnace is employed, we have the direct influence 

 of a highly trained theorist, who concluded his address as Pre- 

 sident of this Association in 1882 by reminding us that "in the 

 great workshop of Nature there is no line of demarcation to be 

 drawn between the mo>t exalted speculation and commonplace 

 practice." The recent introduction of the method of healing by 

 radiation is, of course, the result of purely theoretical con- 

 siderations. 



The progress in the methods of extracting the precious metals 

 has been very great, both on the chemical and engineering sides, 

 but it is curious that in the metallurgy of gold and silver, many 

 ancient processes survived which were arrived at empirically — 

 a noteworthy exception being presented by the chlorine process 

 for refining gold, by the aid of which many millions sterling of 

 gold have been purified. The late Mr. H. B. Miller based this 

 process for separating silver from gold on the knowledge of the 

 fact that chloride of gold cannot exist at a bright red heat. The 

 tension of dissociation of chloride of gold is high, but the precious 

 metal is not carried forward by the gaseous stream, at least not 

 while chloride of silver is being formed. 



The influence of scientific investigation is, however, more 

 evident in that portion of the metallurgic art which deals with 

 the adaptation of metals for use, rather than with their actual 

 extraction from the ores. 



Only sixteen years ago Sir Nathaniel Barnaby, then Director 

 of Naval Construction, wrote, " Our distrust of steel is so great 

 that the material may be said to be altogether unused by private 

 ship-builders, . and marine engineers appear to be equally 



afraid of it." He adds, " The question we have to put to the 

 steel makers is, What are our prospects of obtaining a material 

 which we can use without such delicate manipulation and so 

 much fear and trembling?" All this is changed, for, as Mr. 

 Eigar informs me, in the year ending on June 30 last, no less 

 than 401 .ships, of three-quarters of a million gross tonnage, 

 were being built of steel in the United Kingdom. 



Why is it, then, that steel has become the mateiial on which 

 we rely for our ships and for our national defence, and of which 

 such a splendid structure as the Forth Bridge is constructed ? 

 It is because, side by side with great improvement in the quality 

 of certain varieties of steel, which is the result of using the open- 

 hearth process, elaborate researches have shown what is the 

 most suitable mechanical and thermal treatment for the metal ; 

 but the adaptation of steel for industrial use is only typical, as 

 the interest in this branch of metallurgy generally appears for 

 the moment to be centred in the question whether metals can, 

 like many me'alloids, pass under the application of heat or 

 mechanical stress from a normal state to an allotropic one, or 

 whether metals may even exist in numerous isomeric states. 



It is impossible to deal historically with the subject now, further 

 than by stating that the belief of more than one "modification" 

 is old and widespread, and was expressed by Paracelsus, who 

 thought that copper "contains in itself its female," which could 

 be isolated so as to give " two metals" ..." different in their 

 fusion and malleability " as steel and iron differ. Within the 

 last few years Schiitzenberger has shown that two modifications 

 of CO) per can exist, the normal one having a density of 895, 

 while that of the allotropic modification is only 80, and is 

 moreover rapidly attacked by dilute nitric acid, which is without 

 action on ordinary copper. It may be added that Lord Ray- 

 Icigh's plea for the investigation of the simpler chemical reactions 

 has been partly met, in the case of copper, by the experiments 

 conducted by V. H. Veley on the conditions of chemical chi.nge 

 between nitric acid and certain metals. 



Bergmann, 1781, actually calls iron polymorphous, and says 

 that it plays the part of many metals, " Adeo ut jure dici queat 

 poljmorphum ferrum plurium simul metallorum vices suslinere." 

 Osmond has recently demonstrated the fact that at lea;t two 

 modifications of iron must exist. 



Prof Spring, of Liege, has given evidence that in cooling 



NO. II 39, VOL. 44] 



