and tlie Mode of its Communication. 45 



passed through the vertical sides of the instrument in 

 45! minutes, in the experiment, must have amounted 

 to 5885 parts. For, the whole of the surface of the 

 instrument, = 85.195 superficial inches, is to the whole 

 of the heat given off, = 10,000, as the surface of the 

 vertical sides of the instrument, = 50.136 superficial 

 inches, to the quantity of heat which must have passed 

 off through that surface in the given time, = 5885. 



Now, as we may with safety conclude that the quan- 

 tity of heat which passes off through a given surface 

 must be as the times elapsed, all other circumstances 

 being the same, we can determine how much of the heat 

 given off by the instrument, in those experiments in 

 which its ends were covered, passed through the sides 

 of the instrument ; and, consequently, how much of it 

 must have made its way through its ends and neck, not- 

 withstanding their being covered: 



The instrument with its ends and neck covered up 

 with eider-down, furs, &c., was found to cool through 

 the standard interval of 10 degrees in 55! minutes. 

 Now, as only 5885 parts of heat were found to pass 

 through the naked vertical sides of the instrument in 

 45 \ minutes, no more than 7015 parts could have 

 passed through the same surface in 55^ minutes ; con- 

 sequently, the remainder of the heat lost by the instru- 

 ment in the experiment in question, amounting to 

 2985 parts, must necessarily have made its way through 

 the covered ends and neck of the instrument in the 

 given period, 55} minutes. 



Taking it for granted that these computations are 

 well founded, we may now proceed to a more exact de- 

 termination of the relative quantities of heat which 

 made their way through the sides of the instrument 



