60 CALORIFIC POWER OF FUELS. 



cient oxygen to pass in for the required pressure. Close the 

 cock of the oxygen cylinder, carefully close the conical cock, 

 and break the connection between the bomb and the oxygen 

 cylinder. The substance, especially if coal, must not be too 

 fine, and the oxygen must flow in very slowly to avoid blow- 

 ing any of it from the capsule. 



The bomb thus prepared is placed in the calorimeter, and 

 the thermometer and agitator adjusted. Pour in the previously 

 weighed water, agitate a few minutes to restore equilibrium of 

 temperature, and commence the observations. 



The experimenter notes the temperature minute by minute 

 for four or five minutes, and determines the rate of the ther- 

 mometer before the combustion. Then he joins the elec- 

 trodes, and the combustion begins immediately, almost instan- 

 taneously; but the transmission of. heat to. the calorimeter 

 takes some time. 



The temperature is taken one-half minute after kindling, 

 then at the end of the minute, then at each minute to the 

 time when the thermometer begins to lower regularly. This 

 is the maximum. The observations are continued for a few 

 minutes more to ascertain the rate of fall of temperature. 



We now Tiave all the elements needed for the calculation, 

 and particularly for the "single correction necessary to make 

 tinder the circumstances. This is the correction for loss of 

 heat before reaching the maximum temperature, which is 

 quite small considering the short time and the large mass in- 

 volved. 



It is not necessary to use the corrections of Regnault and 

 Pfaundler with this apparatus. Newton's law of cooling gives 

 sufficiently accurate results, even in rigorous investigations. 

 Special experiments made ., to determine the rate of cooling of 

 the water in the calorimeter, when the apparatus was set up as 

 usual, showed that the correction may be regarded as follow- 

 ing a simple law, but between comparatively large limits, 



