324- DISCOURSE ON THE STUDY 



Magnetism and Electricity. 



(363.) These two subjects, which had long main- 

 tained a distinct existence, and been studied as 

 separate branches of science, are at length effectually 

 blended. This is, perhaps, the most satisfactory 

 result which the experimental sciences have ever 

 \ei attained. All the phenomena of magnetic po- 

 larity, attraction, and repulsion, have at length been 

 resolved into one general fact, that two currents of 

 electricity, moving in the same direction repel, and 

 in contrary directions attract, each other. The 

 phenomena of the communication of magnetism and 

 what is called its induced state, alone remain un- 

 accounted for ; but the interesting theory which has 

 been developed by M. Ampere, under the name of 

 Electro-dynamics, holds out a hope that this dif- 

 ficulty will also in its turn give way, and the whole 

 subject be at length completely merged, as far as the 

 consideration of the acting causes goes, in the more 

 general one of electricity. This, however, does not 

 prevent magnetism from maintaining its separate 

 importance as a department of physical enquiry, 

 having its own peculiar laws and relations of the 

 highest practical interest, which are capable of 

 being studied quite apart from all consideration of its 

 electrical origin. And not only so, but to study them 

 with advantage, we must proceed as if that origin 

 were totally unknown, and, at least up to a certain 

 point, and that a considerably advanced one, conduct 

 our enquiries into the subject on the same inductive 

 principles as if this branch of physics were abso- 

 lutely independent of all others. 



