Royal Society, 65 



k 

 Substance -r=-. 

 cv 



Oil 1-37 



Melted sulphur . . . 1*68 



Ice 13-5 



Snow ...... 4*2 



Frozen soil 10- 8 



Sandstone 16*0 



For oil we may call cD = 0*26, which will give k = 035 for 

 this substance ; and its electric conductibility will be 0*02 if it 

 be shown that Wiedemann's law is general. Dr. Matthiessen 

 has found 0*04 for metallic carbon. 

 For ice we have 



cD = 0-5, 

 whence k = 6'7. 



The relative values of snow and frozen earth may serve for a 



future theory of the freezing and thawing of the earth's surface, 



which may lead, perhaps, to an explanation of the glaciers of 



Siberia. Rocks present marked difficulties in respect of their 



calorific conductibility ; and it is indispensable to know them to 



account for the motion of heat in the interior of the globe. 



k 

 Thus, I found -^ =12-9 in a coarse-grained granite, and =7*0 



in a serpentine from Toplitz. 



The only serious difficulty which prevents perfectly accurate 

 results from being obtained by this kind of observation, is the 

 very distinct variation of the conductibilities with the tempera- 

 ture. Unfortunately the theory of heat is still, so to say, in its 

 infancy as concerns the laws according to which these variations 

 take place. 



X. Proceedings of Learned Societies, 



ROYAL SOCIETY. 

 [Continued from vol. xxiv. p. 660.] 

 March 27, « rpHEORETICAL Considerations on the Conditions 

 1862. •*- under which the Drift Deposits containing the 



Remains of Extinct Mammalia and Flint-implements were accumu- 

 lated j and on their Geological Age." By Joseph Prestwich, Esq., 

 F.R.S., F.G.S. 



April 3. — Major- General Sabine, President, in the Chair. 



The following communications were read : — 



"On the Law of Expansion of Superheated Steam." By William 

 Fairbairn, Esq., LL.D., F.R.S., and Thomas Tate, Esq. 



In a former paper selected for the Bakerian Lecture, entitled 

 Phil. Mag. S. 4. Vol. 25, No. 165. Jan. 18G3. F 



