282 PROCEEDINGS OF THE AMERICAN ACADEMY 



of the angle of rotation. This effect is, however, complicated by the 

 variation in the distance of the different parts of the two coils from 

 each other which attends this rotation. It is accordingly found that 

 the curve which represents the actual variations in intensity (obtained, 

 according to Fisk's method, by measuring with the galvanometer the 

 intensity of single induction shocks at every ten degrees of revolution 

 of the secondary coil *) differs from the curve of cosines in being 

 slightly convex towards the abscissa just before it reaches that line. 



The scale with wliich the instrument is provided indicates the in- 

 tensity of the induced current at different positions of the secondary 

 coil, expressed in terms of an arbitrary unit employed in the gradua- 

 tion of a large " sledge apparatus," in use at the physiological labora- 

 tory, and similar to the unit adopted in German laboratories for the 

 graduation of similar instruments. 



* See Cyon's Metliodik der physiologischen Experimente, p. 379. 



