Electromagnetic Induction. 



331 



curves of constant positive or negative induction lying on 

 opposite sides of the curve of no induction ; and it is the re- 

 sults of experiments made for this purpose, along with those 

 of others which were made for the purpose of tracing some of 

 the curves of constant induction between the coils with their 

 axes perpendicular to each other, which I have now to bring 

 before the Society. 



The arrangement of the apparatus and the nature of the 

 experiments will be easily understood by reference to the an- 

 nexed diagram. 



A, B, C, and D are four coils of wire made as nearly iden- 



tical in all respects as possible. Each coil consists of 182 turns 

 of No. 24 silk-covered copper wire, of O065 centim. diameter, 

 wound in a rectangular groove in a flat wooden reel. The 

 inner circumferences of the coils are 21*95 centim. ; their 



