282 Dr. H. F. Weber on the Specific Heat of 



For the calculation of this y -value it is assumed that the spe- 

 cific heat of graphite, within the temperature-intervals 550° to 

 750°, 750° to 900°, and 900° to 1050°, changes linearly with 

 the temperature ; it is therefore allowable to write 



&c. &c. 



and to deduce the following mean values : — 



2/ 822<0 =0-4539, 



2/ 977 . 9 =0-4670. 



A comparison of these numbers with those deduced for dia- 

 mond, viz. 



2W 7 = 0-4408 > 

 &W 5 =0-4489, 



3Wo=0-4589, 



leads to the following conclusions : — 



(1) The increase of the specific heat with the temperature, 



Ay . 

 . fp, is 

 A I For graphite. For diamond. o 



0-0000472 0-0000405 between 600 and 800 



0-0000840 0-0000561 „ 800 ,,1000 



Mean . 0-0000656 0-0000483 



whether the values of -rl, for graphite and diamond, really in- 

 crease within the temperature-interval |600° to 1000°, and 

 whether the values are different for graphite and diamond, I 

 cannot with certainty decide. An experimental error in the 

 direct determination of W£ , amounting to 1 per cent, too much 

 or too little, would influence the value assigned to y T so as to 



A?/ 

 falsify the true value of the quotient ■— as much as 100 per 



A-?/ 

 cent. As the differences between the above four values of -r-^ 



AT 



amount at the most to 50 per cent, of the value of this expression, 



and as the magnitude of WJ is not determined to within less 



than \ per cent, of its value, the magnitude of -r—- may very well 



be independent of the temperature from 600° and upwards ; and 

 the value of this expression may be exactly the same for both 

 modifications of carbon. Inasmuch, however, as the experi- 



