Section III., 1911. [17] Trans. R.S. C. 
On the Relation Between the Adiabatic and Isothermal Young’s Moduli 
of Metals. 
E. F. Burton, B.A. (Cantras.), PH. D. (Tor.) 
Presented by Professor J. C. McLennan. 
(Read May 17, 1911.) 
In the ordinary equation for the velocity of sound in solids, viz., 
AT 
= à = where q’ is Young’s modulus for the substance and d is the 
density, the Young’s modulus considered is that which comes into play 
when the change in strain takes place so rapidly that the heat produced 
or absorbed during the strain has not time to escape. Lord Kelvin! 
has shown that this Young’s modulus should be connected with the 
Young’s modulus (q) found by statical methods such as stretching 
wires or bending rods, by the following equation :— 
il sheen! wT 
Gr, 1G J Kd 
where w is the coefficient of linear expansion of the metal, T, the 
absolute temperature, J, the mechanical equivalent of heat, K, the 
specific heat of the substance, and d its density. 
The above equation gives at once the ratio of q’ to q. In Table I 
the values of q for several metals experimented on by Wertheim * are 
given in column I, and the corresponding values of q’/q deduced from 
the above equation in column 2. 
TABLE I. 
q in dynes per sq. em. q’/q deduced from the 
Substance. QUO above equation. 
LTE Sly A +... 8-56 1-008 
LST esc Poles eos: A a a a 4-09 1-00362 
DEVENUE. Gi 2 EAN rx) 7-22 1-00315 
Copper 12-20 1-00325 
ERG catch: Bre pee LEA AN ne A ae 1-74 1-0031 
Gildas NS ERNST RE Rie à ake 6-02 1-0006 
la) RM clerc aig ot Rm Os duce à 18-24 1-00259 
PTAGUMUINS ee eee er ees 16-7 1-00129 
1 Article on Elasticity, Encyclopaedia Britannica. 
2 Wertheim, Annales de chim. et de phys., 1844. Pogg. Ann. 77, 427, 1849. 
