NOMOS. 



81 



When a magnetic needle is placed in the imme- 

 diate neighbourhood of an electrical conductor, it 

 arranges itself across that conductor. 

 This is a familiar fact, and one not at 

 all difficult to understand, if it be assumed 

 that the needle is surrounded by trans- 

 verse currents of electricity. 



A magnetic 

 needle must 

 arrange itself 

 across an 

 electrical 

 conductor. 



Fig. 22. 



Let MM' be a magnetic needle lying upon an 

 electrical conductor c c', and moving upon a central 

 pivot the position of which is indicated by the dot. 

 Let the currents in the conductor and the currents 

 in the magnet travel in the direction which is indi- 

 cated by the arrows placed upon each, and it is 

 evident, according to the premises, that the currents 

 will react upon each other until they are placed in 

 the same direction ; and that they cannot be placed 



Fig. 23. 

 G 



