TRANSACTIONS OF SECTION B. 597 



fusible constituent. A furlher instance is tlius afforded of the fact that a variation 

 of either temperature or pressure will eifect the union of solids. It may be added 

 that B. C. Damien is attempting: to determine what variation in the melting-point 

 of alloys is produced by fusing- them under a pressure of two hundred atmospheres. 

 Italian physicists are also working on the compressibility of metals, and F. Boggio- 

 Lera has recently established the existence of an interesting relation between the 

 coefficient of cubic compressibility, the specific gravity, and the atomic weight of 

 metals. 



Few questions are more important than the measurement of very high tempera- 

 tures. Within the last few years II. le Chatelier has given us a thermo-couple of 

 platinum with platinum containing 10 per cent, of rhodium, by the aid of which 

 the problem of the measurement of high temperatures has been greatly simplified. 

 A trustworthy pyrometer is now at hand for daily use in works, and the liberality 

 of the Institution of Mechanical Engineers has enabled me to conduct an investi- 

 gation which has resulted iu the adoption of a simple appliance for obtaining, in 

 the form of curves, photographic records of the cooling of masses of metal. A 

 report on the subject has already been submitted to a Committee, of which the 

 Director-General of Ordnance Factories is the Chairman ; and Dr. Anderson, to 

 whom I am indebted for valuable assistance and advice, intends to add this new 

 method for obtaining autographic curves of pyrometric measurements to the 

 numerous self-recording appliances used in the (rovernment factories which he 

 controls. It has proved to be easy to ascertain, by the aid of this pyrometer, 

 what thermal changes take place during the cooling of molten masses of alloys, 

 and it is possible to compare the rate of cooling of a white-hot steel ingot at defi- 

 nite positions situated respectively near its surface and at its centre, and thus to 

 solve a problem which has hitherto been considered to be beyond the range of 

 ordinary experimental methods. Some of the curves already obtained are of much 

 interest, and will be submitted to the .Section. It is probable that the form of the 

 curve which represents the solidification and cooling of a mass of molten metal 

 aflbrds an exceedingly delicate indication as to its purity. 



Prof II. E. Armstrong holds that the molecules of a metal can unite to form 

 complexes with powers of coherence which vary with the presence of impurity, 

 Crookes, by a recent beautiful investigation, has taught us how electrical evapora- 

 tion of solid metals maybe set up in vacuo, and has shown that even an alloy may 

 be decomposed by such means. We may hope that such work will enable us to 

 understand the principles on which the strength of materials depends. 



Before leaving the consideration of questions connected with the molecular 

 constitution of metals, I would specially refer to the excellent work of Ileycock 

 and Neville, who have extended to certain metals with low melting-points Raoult's 

 investigations on the effect of impurity on the lowering of the freezing-point of 

 solids. With the aid of one of my own students, H. C. Jenkins, I have further 

 extended the experiments by studying the effect of impurity on the freezing-point 

 of gold. Ramsay, by adoptinfj: Raoult's vapour-pressure method, has been led to 

 the conclusion that when in solution in mercury the atom of a metal is, as a rule, 

 identical with its molecule. The important research on the liquation of alloys has 

 been extended by E. ]\Iattbey to the platinum-gold and palladium-gold series, in 

 which the manipulation presented many difficulties ; and E..I. Ball has .studied the 

 cases presented by the antimony-copper-lead series. Dr. Alder Wright has con- 

 tinued his own important investigation upon ternary alloys, and A. P. Laurie has 

 worked on the electro-motive force of the copper-zinc and copper-tin and gold-tin 

 series, a field of research which promises fruitful results. 



In no direction is advance more marked than in the mechanical testing of 

 metals, in which branch of investigation this country, guided hy Kirkaldy, un- 

 doubtedly took the leadins* part, and in connection with which Kennedy and Unwin 

 have established world-wide reputations. I would also specially mention the work 

 which has been carried on at the Government testing works at Berlin under Dr. 

 Wedding, and the elaborate investigations conducted at the Watertown Arsenal, 

 Massachusetts, not to mention the numerous continental testing laboratories directed 



