282 PROCEEDINGS OF THE AMERICAN ACADEMY 



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

 A'ariation in the distance of the different pai-ts 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 Fis^k's method, by measuring with the galvanometer the 

 intensity of single induction shocks at eveiy 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 which 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 Methodik der physiologischen Experimente, p. 379. 



