202 University of California Publications. [Geology 



In the case of the heat and light conductivities of crystalline 

 bodies, we assume the properties of the ether to be affected by 

 this molecular structure. Increased conductivity in one direc- 

 tion is explained by an increase in the elasticity e of the ether 

 in that direction, the density d remaining constant (Fresnel) ; or, 

 equally well, by a decrease in the density, the elasticity being 

 constant and equal to infinity (Kayleigh) or equal to -K (Thom- 

 son) where E corresponds to the modulus of shear or coefficient 

 of rigidity. This is in accordance with the old elastic solid 

 theory where V = yJ ^ ■ The modern electro-magnetic theory of 



Clerk Maxwell teaches that V^-^-^-, where K is the specific 

 inductive capacity and y is the permeability, and the value of 



this radical increases with an increase in — or with a decrease 



y 



in K. Whichever one of these views we adopt, we assume always 

 fundamentally that some property of the ether is affected by 

 any regularity in the arrangement of the molecules. ' If we 

 arrange a number of material particles in orderly fashion we 

 have not affected the properties of the ether; if, as is probably 

 the case in crystalline solids, we arrange a number of aggre- 

 gates consisting of many molecules each in orderly fashion, we 

 have affected the properties of the ether. Where is the dividing 

 line ? The question that suggested itself was this : If light 

 and heat conductivity in a crystal are functions of internal 

 molecular structure and of conditions of internal strain, will the 

 heat and light conductivity of a rock depend similarly, in part, 

 at least, upon its internal crystallographic structure and its con- 

 ditions of internal strain? 



In a schist which has been dynamically metamorphosed, we 

 assume that the internal strain has been relieved by the re- 

 crystallization of the constituent minerals ; but this recrystalliza- 

 tion has set up in the rock a definite crystallographic structure 

 comparable to the definite molecular structure of a crystal. 

 Will this structure in itself affect the thermal conductivity of 

 the rock ? Can we here consider the crystal as the physical unit 

 even as we have heretofore considered the molecule or aggrega- 

 tion of molecules? 



