184 Prof. Frankland on the Origin of Muscular Power. 



steeped in potassic chlorate and dried, was inserted in the mix- 

 ture. The temperature of the water in the calorimeter was now 

 carefully ascertained by a delicate therm ometer, and, the end of 

 the cotton thread being ignited, the tube with its contents was 

 placed in the copper bell and lowered to the bottom of the 

 water. As soon as the combustion reached the mixture, a stream 

 of gases issued from numerous small openings at the lower edge 

 of the bell and rose to the surface of the water — a height of 

 about 10 inches. At the termination of the deflagration, the 

 water was allowed free access to the interior of the bell, by open- 

 ing 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 repeat- 

 edly, 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 gives the calorific power, or the 

 potential energy, of the substance consumed, expressed as heat. 

 The value thus obtained^ however, is obviously subject to the 

 following corrections : — 



1. The amount of heat absorbed by the calorimeter and ap- 

 paratus 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 chlo- 

 rate 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 atmo- 

 sphere : to be added. 



Although the errors due to these causes to some extent 

 neutralize each other, there is still an outstanding 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 all ex- 

 perimentally determined, and was added to the increase of tem- 

 perature observed in each experiment. 



The amount of heat carried away by the escaping gases after 

 issuing from the water may be divided into two items, viz. : — 



a. The amount of heat rendered latent by the water which is 

 carried off by the gases in the form of vapour. 



/3. The amount of heat carried off by these gases by reason 

 of their temperature being above that of the water from which 

 they issue. 



It was ascertained that a stream of dry air passed through 

 the water of the calorimeter at about the same rate and for the 



