384 ANALOGY OF IMPONDERABLE AGENTS. [SECT. xxxv. 



are quite sufficient to account for what were supposed to 

 be their distinctive qualities. He has given still greater 

 assurance of their identity by showing that the magnetic 

 force and the chemical action of electricity are in direct 

 proportion to the absolute quantity of the fluid which 

 passes through the galvanometer, whatever its intensity * 

 may be. 



In light, heat, and electricity, or magnetism, nature has 

 exhibited principles which do not occasion any appreciable 

 change in the weight of bodies, although their presence is 

 manifested by the most remarkable mechanical and chemical 

 action. These agencies are so connected, that there is reason 

 to believe they will ultimately be referred to some one power 

 of a higher order, in conformity with the general economy 

 of the system of the world, where the most varied and 

 complicated effects are produced by a small number of 

 universal laws. These principles penetrate matter in all 

 directions ; their velocity is prodigious, and their intensity 

 varies inversely as the squares of the distances. The de- 

 velopment . of electric currents, as well by magnetic as 

 electric induction, the similarity in their mode of action in 

 a great variety of circumstances, but, above all, the produc- 

 tion of the spark from a magnet, the ignition of metallic 

 wires, and chemical decomposition, show that magnetism 

 can no longer be regarded as a separate independent prin- 

 ciple. Although the evolution of light and heat during the 

 passage of the electric fluid may be from the compression 

 of the air, yet the development of electricity by heat, the 

 influence of heat on magnetic bodies, and that of light on 

 the vibration of the compass, show an occult connexion 

 between all these agents, which probably will one day be 

 revealed. In the mean time it opens a noble field of ex- 

 perimental research to philosophers of the present, perhaps 

 of future ages. 



