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XI. On the Structure of Metals, its Origin and Changes . 
By M. F. Osmond and Professor Roberts-Austen, C.B., F.R.S. 
Received June 10,—Read June 18, 1896. 
[Plates 9, 10.] 
It has been shown by Herbert Tomlinson that the atomic volume of metals is 
intimately connected with their thermal capacity'" and with Young’s modulus.! He 
considers in view T of the work of Wertheim,! of Maxwell, § and of Heen,|| and as 
the result of his own experiments, that the value of the product of the elasticity E, 
when multiplied by a fractional power of the atomic volume, A/D, is a constant for 
all metals. E (A/D) 73 = 181 X 10 4 . The divergencies shown by several metals from 
this mean value arise from the fact that the presence of small amounts of impurity 
makes a great difference in their elasticity. 
Sutherland^ finds a close relation between the atomic volume and the rigidity 
of metals, and considers that this rigidity is “ in its essence a kinetic phenomenon 
almost as simple in character as the elasticity of perfect gases.” 
Professor Fessenden, moreover, has urged that the cohesion of metals is 
proportional to some power of the atomic volume, and he considers that the rigidity 
varies as the fifth power of the distance of the centre of the atoms, or as (atomic 
volume) 673 . These facts are given merely to show that the atomic volume of the 
added element is very important. 
Some years ago, one of us purified gold with great care and alloyed seventeen 
separate portions of it with foreign elements, in quantities which were in all cases 
close to 0'2 per cent., and from each sample of this alloyed gold, bars were cast 
88 millims. long by 7'5 millims. wide by 5 - 2 millims. thick. The metal was in each 
case poured into a closed iron mould heated to about 500°; the cooling was therefore 
not very rapidly effected. The tensile strength, elongation, and reduction of sectional 
* ‘ Roy. Soc. Proc.,’ vol. 38 (1884-85), p. 488. 
t ‘Roy. Soc. Phil. Trans.,’ 1883, p. 32. 
X ‘Ann. de Chim. efc de Phys.,’ vol. 12, 1844. 
§ ‘ Roy. Soc., Phil. Trans.,’ vol. 126, 1866. 
|| ‘ Bull, de l’Acad. Royale de Belgique,’ vol. 4 (1882). 
f ‘Phil. Mag.,’ vol. 32, 1891, p. 41. 
** ‘ Chcm. News,’ vol. 66, 1892, p. 206. 
3 H 
MDCCCXCVI.—A. 
17.8.96 
