166 



Messrs. Bottomley and Tanakadate on the 



vapour formed itself into layers of different temperatures, the 

 parts of the flask nearest the surface of the liquid being the 

 hottest. At a height of 2J inches above the surface of the 

 liquid the temperature was often found to be as much as 8° or 

 10° C. cooler than it was just above the surface. The diffi- 

 culty could, to a certain extent, be overcome by putting a 

 cloak of fine flexible wire gauze all round the upper part of 

 the flask ; but the greatest watchfulness was needed to avoid 

 mistakes. 



In order to reduce the results obtained from the readings 

 of the galvanometer to absolute electromagnetic measure, a 

 carefully prepared standard Daniell's cell was kept with its 

 current always flowing through a known high resistance : and 

 from time to time the galvanometer which was being used was 

 thrown into the circuit, and the value of the galvanometer- 

 deflexion determined. The electromotive force of the Daniell's 

 cell was valued at 1*072 volt. 



The results obtained are shown in the accompanying curves 

 and tables. 



7X105 



6 „ 



» 5 



.•a 



■■HI M 



)° 100° 120° 140° 160° 180° 200° 220° 240° 260° 



In the curves the electromotive forces are shown as ordi- 

 nates, the differences of temperature between the hot and cold 



