PEIRCE AND WILLSON. — THKRMAL CONDUCTIVITIES, 



39 



several years of experimeutatiou, is entirely different. An iron casting, 

 Z, seen in plan in Figure 11 and in elevation in Figure 9, accurately 

 planed below and turned true above, is the bottom of the box. Be- 

 tween this casting (which can be bolted to ^ as Z) is in Figure 6) and 



Figure 



A is held the prism to be experimented on. While Z was in the lathe 

 a small hole, i/, about 3 millimeters in diameter and 4 millimeters deep 

 was drilled exactly in the centre of its upper face. Subsequently a piece 

 of solid drawn brass tube 12.3 era. in outside diameter and 13.5 cm. high, 

 with carefully squared ends, was held centrally in Z, by means of a 



