DETERMIXATIOX OF THE THERMAL COXDaCTrVITV OF MARBLE, 273 



The following diagi'am shows tlie relation between S and D. 



Curve showing relation between D and S. 





From the diagram, it is easy to see that for a value of D, there 

 are infinite number of values of S. lUit we are enabled to select the 

 proper value by comparison with that obtained from the value of a. 



Out of many experiments, the following two are taken as speci- 

 mens. In the first, the period was 50 minutes or 3,000 seconds, and the 

 readings were taken during the 8th period from the beginning of the 

 cyclical operation. It was found, that after the (ith period, the mean 

 value of the temperature at a point I'emained sensibly constant, or in 

 other words the trace of the initial distribution of temperature was 

 com[)letely effaced, so far at least as experiment can tell us. The 

 experiment was conducted according to the potentiometer method. 



