354 



On the Specific Heat of Basalt. 



of a small gas-furnace, in others in a coke-furnace. All the 

 former were consistent with each other, and those of the latter 

 group in which fresh specimens of basalt were used were in 

 agreement with them. The results obtained with specimens 

 which had been heated two or more times in the coke-furnace 

 were, however, very irregular, and have been discarded. 



As we have not definitely proved wdiat was the cause of 

 these discrepancies, we publish our conclusions with a certain 

 amount of reserve. 



In the following table T is the temperature (Cent.) of the 

 basalt at the moment of immersion, C is the mean specific 

 heat between about 20° C and T. 



T. 



C. 



T. 



C. 



467 



0-199 



860 



0-277 



747 



•217 



924 



•282 



759 



•223 



977 



•284 



792 



•220 



983 



•283 



846 



•257 



1090 



•285 







1192 



•290 



These results are plotted in the figure. 



•30 









•28 









'2b 









•24 









•22 







| ggjgQH Bi BBBH1 1 



400 



500 



600 



700 



800 



900 



1000 



1100 



1200 



If C 12 be the mean specific heat between two temperatures 

 t x and t 2 we have the relation 



Ou{h-t,) =C 12 (t 2 -t i ) +C 2Z {t s -t 2 ). 



If, then, we take the mean specific heat from 20° C. 



to 470° to be -199 

 to 750 „ -216 



to 880 „ -278 

 and to 1190 „ '290 



we get the following results : — 



