492 M. Regnault on the Specific Heat of Simple Bodies, 



c, the unknown specific heat of the substance ; 

 we have 



(MC+jo)(T-^) = AA(9'. 



Let us suppose that during the first period of three minutes 

 the temperature of the calorimeter is inferior to that of the sur- 

 rounding air; it will undergo an increase of heat a. If, on the 

 contrary, this temperature is, during the last period of three 

 minutes, higher than that of the surrounding air, the calorimeter 

 would be cooled by a quantity a'. It was admitted that for from 

 3 minutes to 3^ minutes the calorimeter continued to undergo 

 the same variation of temperature as in the three preceding 



minutes, and that it would undergo an elevation of temperature ^. 



At 3^ minutes the basket was immersed in the calorimeter ; it 

 was supposed that from 3^ to 4 minutes the temperature of the 

 calorimeter was not influenced by disturbing causes, because 

 during this period the calorimeter traversed almost completely 

 its variation of temperature. From 4 minutes to 7 minutes the 

 temperature did not change sensibly, and it might be admitted 

 that the perturbation produced by external causes was equal to 

 that exhibited during the three succeeding minutes, that is from 

 7 to 10 minutes. 



According to that we should have 



o 



This mode of proceeding is only suited for bodies which are 

 good conductors of heat ; for others, a tolerably long time is 

 necessary before the thermometer of the calorimeter attains its 

 stationary temperature. It is hence necessary to calculate the 

 change of temperature which external causes prodjice during 

 each minute. If t and i' represent these surrounding tempera- 

 tures during the initial and terminal periods of three minutes, 

 we might put 



^=A(e'-i') + K, 



A and K being the constants which would be determined by the 

 experiments themselves. The variation of temperature produced 

 in each minute for a temperature t of the calorimeter, and an 

 external temperature t, would be 



A(^-/) + K. 



