Vol. 4] Th el en.— Thermal Conductivities of Certain Schists. 205 



the bending' test can not be applied here and no other method 

 has been successfully substituted for it. Mica shows less varia- 

 tion in the basal planes and values perpendicular to this have 

 also not been worked out. The physical constants of horn- 

 blende have not yet been determined. These two minerals will 

 doubtless show much greater differential effects than the quartz 

 does, and they are of more than theoretical importance. 



The volume relations are interesting as they give an idea of 

 the relative insignificance of the synclinal and anticlinal de- 

 formations necessary to relieve the strains set up by thermal 

 changes. If we imagine a cubic mile of quartz similar to the 

 cubic foot discussed and heat this up for a thousand degrees, we 

 get the expansion in the two directions (assuming rather dubi- 

 ously that Fizeau's values for the coefficients of expansion as 

 determined for the range from 0° to 100° hold for this range 

 as well) to be 



5280X-0078=41.2 ft. parallel to c, and 

 5280X-014 =73.9 ft, perpendicular to c. 



A similar block of augite would give expansions of 84.5, 32.7 

 and 96.0 ft. per mile in the three directions which correspond 

 to the three main axes of thermal expansion. Calcite shows 

 much greater discrepancies since c is negative in one direction, 

 the values being 



Zt = 7o (1 + 0.0425 t + 0.0708 f) for parallel to e. 

 7 t = 7o (1 — 0.04057 t + 0.0704 f) for perpendicular to c. 

 Hence the expansion for a thousand degrees (making the same 

 dubious assumptions) would be 



5280 X ( .025 + .008) = + 176 ft. 

 5280 X ( — .0057 + .004) = — 8.9 ft, 

 Again, one result of the differential thermal conductivities is its 

 effect upon the outlines of the zone within which the metamorphic 

 influence of an intrusive magma would make itself felt. 



THE USE OF THE WAX-FIGURE FOR THE DETERMINATION OF THE 

 RELATIVE HEAT CONDUCTIVITIES. 



J. Ingen-Houtz* was the first to suggest the use of wax- 

 figures. His work was done over a hundred and twenty years 



* J. Ingen-Houtz. Sur les metaux comme conducteurs de la chaleur. 

 Jour, de phys. 34, 1789. 



