400 HENRY A. EOWLAND 



original apparatus. In the calorimeter a stirrer was used, so that the 

 basket and water should rapidly attain the same temperature. The water 

 was weighed before and after the experiment, to allow for evaporation. 

 A correction of about 1 part in 1000 was made, on account of the heat 

 lost by the basket in passing from the apparatus to the calorimeter, in 

 the 100 series, but no correction was made in the other series. The 

 thermometers in the calorimeter were Nos. 6163 and 6166 in the dif- 

 ferent experiments. 



The principal difficulty in the determination is in the correction for 

 radiation, and for the heat which still remains in the basket after some 

 time. After the basket has descended into the water, it commences to 

 give out heat to the water; this, in turn, radiates heat; and the tempera- 

 ture we measure is dependent upon both these quantities. 



Let T = temperature of the basket at the time t 



i( IT" _ (I (( 



JW <- 



" " " water t 



Ql __ Q 



(I Q'l __ ( (( (( QO 



6" = T". 

 We may then put approximately 



TT" = (T - T")e-~z, 

 where c is a constant. But 



rpl rpn rpi rp 



0" 0' ' ' Q tf ' 



hence 



To find c we have 



1 0" 0' 



t 3 ff' 



where 6" can be estimated sufficiently accurately to find C" approxi- 

 mately. 



These formulae apply when there is no radiation. When radiation 

 takes place, we may write, therefore, when t is not too small, 



00' = (0" #')(! - e-~T) 



where is a coefficient of radiation, and t is a quantity which must be 

 subtracted from t, as the temperature of the calorimeter does not rise 



