OF ARTS AND SCIENCES. 63 



''[^+^] = ^'-^'^' 



At the limit we find the quantity of heat that passes through when 

 the temperature of the water is t 



From the first and second curve Dj-t^ and D^t^ are easily obtained, 

 and as all the other quantities are known, A" can be determined. 



In my experiment I used for the outer vessel a tin can 7.1 cm. in 

 height. Tliis was covered with the exception of a hole in the top, 

 around which was a collar. In this hole was placed a large test-tube 

 of glass which just fitted the hole. The space between the test-tube 

 and the walls of the can was filled with sand. This was placed in a 

 larger tin can almost full of water, and suspended about 4 cm. from 

 the bottom by a string. Steam was passed from a retort into the test- 

 tube, and several times during the experiments I placed a thermometer 

 in the test-tube, and it always showed that the temperature was 100° C 



At the start the water was 23.3°. I took down the temperatures 

 every minute for almost an hour, but as I do not use these in con- 

 structing the curve, I give only the temperature determined every 

 five minutes, after the first hour : — 



The temperature of the air was 23.3°. The curve given by these 

 points is not very regular ; it changes several times from concave to 

 convex. I therefore determined to take a small arc, find its equation, 

 and investigate the conductivity as given by this arc. I considered 



only the points 



7.4, 8.0, 8.5, 9.0, 9.5, 10.0. 



If five small divisions of the co-ordinate paper are taken as one unit, 

 an equation of the fifth degree, satisfying these six points, is found 

 from : — 



