90 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Diagram of Apparatus. 



The glass part at the left of the diagram is drawn about one third of the actual 

 size. The remainder of tlie apparatus is not drawn to scale, being annexed 

 merely to show the connections. For explanation, see page 91. 



The cell was immersed in a thermostat which could be maintained 

 constant at any desired temperature within one tenth of a degree. 



The electromotive forces were measured by means of an astatic gal- 

 vanometer according to the Poggendorff method. An Ostwald * " poten- 

 tial box," the resistances of which were carefully verified, was connected 



* Ostwald, Hand- und Hilfsbuch, p. 252. 



