474 Royal Society ; — 



over, not acquired instantly; and it is wholly impossible that 

 when the compression takes place in unconfined air, in which the 

 free caloric has liberty to disperse to any extent, the temperature 

 acquired under the same compression can be the same as in that 

 experiment. For all these reasons I conclude that Prof. TyndalFs 

 experiments are entirely favourable to my views, and that La- 

 place's theory is inadequate to account for the observed velocity 

 of sound ; and as I am entitled to infer, from the long silence 

 mathematicians have maintained on this subject, that the mathe- 

 matical part of the old theory is untenable, I hope not to have 

 again the trouble of discussing this question. 



Cambridge, Nov. 17, 1862. 



LXIV. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p, 406.] 



January 23, 1862. — Major-General Sabine, R.A., President, in the 



Chair. 



PT^HE following communications were read : — 

 ■*■ "Contributions towards the History of the Monamines. — 

 No. V. Action of Chloracetic Ether on Triethylamine and Triethyl- 

 phosphine. ,, By A. W. Hofmann, LL.D., F.R.S. 



"Additional Observations and Experiments on the Influence of 

 Physical Agents in the Development of the Tadpole and the Frog." 

 By John Higginbottom, Esq., F.R.S. 



"Note on Internal Radiation." By George G. Stokes, M.A,, 

 Sec. R.S. 



In the eleventh volume of the 'Proceedings of the Royal Society/ 

 p. 1 93*, is the abstract of a paper by Mr. Balfour Stewart, in which he 

 deduces an expression for the internal radiation in any direction within 

 a uniaxal crystal from an equation between the radiations incident 

 upon and emerging from a unit of area of a plane surface, having an 

 arbitrary direction, by which the crystal is supposed to be bounded. 

 With reference to this determination he remarks (p. 196), "But the 

 internal radiation, if the law of exchanges be true, is clearly indepen- 

 dent of the position of this surface, which is indeed merely employed 

 as an expedient. This is equivalent to saying that the constants which 

 define the position of the bounding surface must ultimately disappear 

 from the expression for the internal radiation.'' This anticipation he 

 shows is verified in the case of the expression deduced, according to 

 his principles, for the internal radiation within a uniaxal crystal, on 

 the assumption that the wave-surface f is the sphere and spheroid of 

 Huygens. 



* Phil. Mag. S. 4, vol. xxiii. p. 328. 



f To prevent possible misapprehension, it may be well to state that I use this term 

 to denote the surface, whatever it may be, which is the locus of the points reached 

 in a given time by a disturbance propagated in all directions from a given point j 



