Vol. 4] Thelen. — Thermal Conductivities of Certain Schists. 207 



that which the orientation of the optical axes of elasticity bears 

 them. 



Senarmont 's values for the ratios of the axes of his wax figure 

 ellipses in sections parallel to c in some uniaxial crystals are 

 given here, and reference will be made to these figures later. The 

 figures of the first column are proportional to the axis parallel to 

 c, and the axis perpendicular to c is taken as unity. 



Quartz 



.76 



1.00 



Tourmaline 



1.27 



] .00 



Caleite 



.90 



1.00 



Rutile 



1.10 



1.00 



These were some of the results of Senarmont 's work, results 

 both general and specific. But this genius of the laboratory was 

 unable to state definitely whether or not there was any relation 

 between the thermometric conductivity in any direction and the 

 length of the radius vector of the ellipsoid in that direction. His 

 results, as interpreted by himself, merely showed that the ther- 

 mometric conductivity varied in the different directions and that 

 the wax figures were symmetrical when there was within the 

 crystal no axis of elasticity which made an oblique angle with 

 the surface. ( In this case, an oval was produced. ) 



We can at once come one step nearer our result by getting 

 the relation between the thermal conductivity K, and the ther- 

 mometric conductivity k. It is apparent that the rise in tem- 

 perature, by means of which thermometric conductivity is 

 measured, will be proportional to the thermal conductivity K, 

 and to the reciprocal of the thermal capacity d-s, where d is the 

 density, and s is the specific heat. 



We have, then, k = E/d-s. 

 This agrees with Tait,* who uses s to represent thermal capacity 

 and writes k = K/s. It also agrees with Gruenstein and Giebe,f 

 who have a 2 =K/d-s, where the thermometric conductivity is 

 expressed by a 2 . Such was probably the authors' intention, since 

 a is generally used for distances, and could in this case be propor- 



*Theory of Heat, Tait. 



t E. Giebe. Tiber die Bestimmung der Warmeleitvermogens bei tiefen 

 Temperaturen. Verh. der D. P. Gesellschaft, 1903. 



