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University of California Publications. 



[Geology 



ago ; although his numerical results were of no value whatever, 

 yet his name is remembered because he was the first to outline 

 the method. He took thin slices of crystals cut so as to have 

 two faces parallel, bored a hole perpendicularly through the 

 center of each one, coated both faces with wax and through the 

 hole ran a needle or wire which could afterward be heated by 

 conduction or by an electric current. 



Sixty years elapsed before anything more was done. Then 

 de Senarmont* took up the work. His results on quartz in par- 

 ticular and on about a score of other minerals in general have 

 become classic, and later investigations through half a century 

 have not cast any doubt upon their accuracy. Senarmont used 

 a silver wire which he heated at one end. The wire was either 

 driven through a hole in the section, or its end was lowered per- 

 pendicularly upon the face of the crystal. The wax surface was 

 shielded from any heat which might radiate from the flame or 

 wire. In his later work, Senarmont used also a hollow tube in 

 place of the silver wire. This was heated by passing a current of 

 hot air through it. 



He found that every section of an isometric crystal and every 

 section pei'pendicular to c of a uniaxial crystal gave circular 

 wax figures. This means for the First System a spherical heat- 

 conductivity ellipsoid, and for the Second and Third Systems 

 an oblate or prolate ellipsoid of revolution with the c axis as 

 the axis of revolution. Further experiments with crystals of 

 the Fourth, Fifth and Sixth Systems gave triaxial ellipsoids in 

 all cases. In the orthorhombic system, the three main axes lay 

 in the pinacoids, and hence were parallel to the crystallographic 

 axes. In the monoclinic system, one axis was parallel to the 

 orthodiagonal ; and in the triclinie, not even one axis was 

 uniquely located by a knowledge of the orientation of the crystal- 

 lographic axes. Thus the orientation of the axes of elasticity 

 for heat conduction bears in every case a relation to the direc- 

 tions of the crystallographic axes which is entirely analogous to 



* The scientific literature of the day is replete with brief outlines of the 

 results of his work. Ann. ehim. phys. 1887, 1848, 1850; Ann. Pogg. 1848, 

 1849, 1850, etc.; Wied. Ann. of the same period. 



