652 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Figure 1. 



fications necessary in the 

 apparatus used for the work 

 on marble, but the proced- 

 ure was much the same. 

 The square, plane-faced slab 

 of the material to be tested, 

 enclosed between two other 

 thin slabs of similar mate- 

 rial, 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 without any of 

 its elaborate system of jack- 

 ets, by Figure 1. The final 

 temperatures at the 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 portion of 

 the colder base of the prism 

 was measured. 



The hot chamber A, which 

 weighed about two hundred 

 kilograms, rested in a thick 

 jacket on a heavy table or 

 stand made to hold it : it 

 was connected directly with 

 one (B) of two stout-walled 

 copper boilers, B and B', 

 each of which held about 

 forty litres of water. A 

 light cup-shaped weight in- 

 verted and laid on a large 

 tube with smooth end which 

 projected above the top of 

 the boiler, acted as a sensi- 



