APPENDIX II. 143 



At the termination of the deflagration, the water 

 was allowed free access to the interior of the bell, 

 by opening a stopcock connected with the bell by a 

 small tube rising above the surface of the water in 

 the calorimeter. The gases in the interior of the 

 bell were thus displaced by the incumbent column 

 of water, and by moving the bell up and down re- 

 peatedly a perfect equilibrium of temperature 

 throughout the entire mass of water was quickly 

 established. The temperature of the water was 

 again carefully observed, and the difference between 

 this and the previous observation determines the 

 calorific power or potential energy, expressed as 

 heat, of the substance consumed. 



The value thus obtained is, however, obviously 

 subject to the following corrections : - 



1. The amount of heat absorbed by the calori- 

 meter and apparatus employed, to be added. 



2. The amount of heat carried away by the 

 escaping gases, after issuing from the water, to be 

 added. 



3. The amount of heat due to the decomposition 

 of the chlorate of potash employed, to be deducted. 



4. The amount of heat equivalent to the work 

 performed by the gases generated in overcoming the 

 pressure of the atmosphere, to be added. 



Although the errors due to these causes to some 

 extent neutralize each other, there is still an out- 

 standing balance of sufficient importance to require 

 that the necessary corrections should be carefully 

 attended to. 



The amount of error from the first cause was once for 



