and the Mode of its Communication* 43 



find out how much of the heat made its escape through 

 the covered ends of the instruments, during the time 

 the instruments were cooling through the interval in 

 question. 



In order to determine that point, I now removed the 

 covering from the ends of the instrument No. i ; and, 

 when it was quite naked, I found, on making the ex- 

 periment, that it cooled through the given interval in 

 45^ minutes. 



When its two ends and its cylindrical neck were cov- 

 ered up with warm clothing, I found, by taking the 

 mean of the results of several experiments, that it re- 

 quired 55J minutes to cool through the same interval. 



On measuring the instrument with care, I found its 

 dimensions as follows : 



Inches. 



Diameter of the body of the instrument, . . = 4.03 

 Length of the body, .'.,. ss 3.96 



Diameter of the neck of the instrument, . . = 0.8 

 Length of the neck, . . . . . = 4- 



The superficies of the different parts of the instru- 

 ment are therefore as follows : 



Superficies of the vertical sides of the body (= 4.03 



X 3-HJ59 X 3-9 6 ) S- 1 3 6 inches. 



Superficies of the flat circular bottom of the instru- 

 ment, (4.03 X 3- I 4 I 59 X ^) = 12.755 inches; de- 

 ducting nothing for that part which is covered by the 

 end of the tube, which serves as a support for the 

 instrument. 



Superficies of the flat circular top of the instrument 

 (after deducting 0.502 of a superficial inch for the cir- 

 cular hole in its centre, made to receive the lower end 

 of the cylindrical neck) = 12.253 inches. 



