and 



the Elements Carbon, Boron, and Silicon, 175 



® P G Atp =0-03232(T-* p ) + 0-0000041 (T a -* p 2 ), (1) 



p 



%^=C (i . T (T-g. (2) 



It were an impossible request to demand for experiments such 

 as these, made at temperatures so high, an accuracy equal to that 

 which attaches to measurements conducted at low temperatures ; 

 sources of error will unavoidably creep in. If by more exact 

 researches Pouillet's expression 



W^=0-03237(T-T )+0-0000041(T 2 -T 2 ) 



be found not wholly correct, this will but slightly alter the re- 

 sults of the experiments described in the present paper. The 

 numerical value attaching to the specific heat of carbon at high 

 temperatures may be somewhat modified ; yet the general result, 

 that the two modifications of carbon have for about 600° an 

 almost identical specific heat, will remain unchanged. 



II. The Specific Heat of Carbon. 



A. Specific Heat of Diamond. 



In my former estimation of the specific heat of diamond* 

 I made use of two clear crystals belonging to the Berlin Mine- 

 ralogical Museum, of the total weight of 1*061 grm. "When 

 this small weight of substance was heated 20° or 30° and brought 

 into the ice-calorimeter, the mercury thread receded not more 

 than 20 to 40 divisions of the scale- tube. From further experi- 

 ments I found that the mercury thread is never moved to the 

 exact point corresponding to the amount of heat developed in 

 the calorimeter, but that it always stops a little before reaching 

 this point. If, then, the total displacement of the mercury- 

 thread be small, this error in the proper position of the thread 

 will cause the results calculated therefrom to be too low. On 

 this account my former determinations of the specific heat of 

 diamond from 0° to 30° were too small. In order to reduce this 

 error to the smallest possible limits, the only plan was to use a 

 larger amount of diamond. Through the kindness of the late 

 Prof. G. Rose, the entire diamond collection belonging to the 

 Berlin University was placed at my disposal. I selected the 

 following stones :- — 



* Ber. der deut. chem. Ges. vol. iv.; and Pogg. Ann. 18/2, part ii. 



