180 JAMES CLEKK MAXWELL 



Tlio methods of tho paper now under discussion 

 were developed further in tho "Treatise on Electricity 

 and Magnetism," published in 1ST;} ; in endeavouring 

 to give some slight account of Maxwell's work, wo 

 shall describe it in the form it ultimately took. 

 ^ The task which Maxwell set himself was a double 

 one ; ho had lirst to express in symbols, in as general 

 a form as possible, the fundamental laws of electro- 

 magnetism as deduced from experiments, chiefly the 

 experiments of Faraday, and the relations between 

 the various quantities involved ; when this was done 

 he had to show how these laws could be deduced from 

 the general dynamical laws applicable to any system 

 of moving bodies. 



There are two classes of phenomena, electric and 

 magnetic, which have been known from very early 

 times, and which are connected together. When a 

 piece of sealing-wax is rubbed it is found to attract 

 other bodies, it is said to exert electric force through- 

 out tho space surrounding it ; when two different 

 metals are dipped in slightly acidulated water and 

 connected by a wire, certain changes take place in tho 

 plates, tho water, the wire, and the space round the 

 wire, electric force is again exerted and a current of 

 electricity is said to How in the wire. Again, certain 

 bodies, such as the lodestone, or pieces of iron and 

 steel which have been treated in a certain manner, 

 exhibit phenomena of action at a distance : they aro 

 said to exert magnetic force, and it is found that this 

 magnetic force exists in the neighbourhood of an 

 electric current and is connected with the current. 



Again, when electric force is applied to a body, tho 



