ON THE THERMAL CONDUCTIVITY OF VULCANITE. 



By B. O. Peirce. 



Presented May 10, 1809. Received August 19, 1§99. 



Last year Dr. R. "W. Willson and I published in these Proceedings 

 an account of some determinations of the thermal conductivities of differ- 

 ent kinds of marble, made by the so called " Wall Method." 



A relatively thin, square, plane-faced slab of the material to be exam- 

 ined, enclosed between two other slabs of the same material, formed 

 a rectangular parallelopiped or prism, which was clamped, and left for 

 many hours, between the steam chest, A, and the ice box, Z, of the 

 apparatus* represented by Figure 1. The final temperatures at the 



Figure 1. 



centres of the faces of the slab to be tested were determined by the aid 

 of thermal elements, and the flux of heat through a definite central por- 

 tion of the colder base of the prism was measured. Figure 2 represents 

 the revolving ice holder, which was kept in motion by the motor, M\ 

 and Figure 3 shows the ice pot used in measuring the heat flux. 



* This was partly constructed with the help of an appropriation from the 

 Rumford Fund of the Academy. 



