] 22 EFFECTS OF COHESION. [SECT. xiv. 



three, &c. For example, one volume or measure of oxygen 

 unites with two volumes or measures of hydrogen in the form- 

 ation of water. 



Affinity, modified by the electrical condition of the particles 

 of matter, has hitherto been believed to be the cause of che- 

 mical combinations. However, Dr. Faraday has proved, by ex- 

 periments on bodies both in solution and fusion, that chemical 

 affinity is merely a result of the electrical state of the particles 

 of matter. Now it must be observed that the composition of 

 bodies, as well as their decomposition, may be accomplished by 

 means of electricity ; and Dr. Faraday has found that this 

 chemical composition and decomposition, by a given current 

 of electricity, is always accomplished according to the laws of 

 definite proportions ; and that the quantity of electricity 

 requisite for the decomposition of a substance is exactly the 

 quantity necessary for its composition. Thus the quantity 

 of electricity which can decompose a grain weight of water 

 is exactly equal to the quantity of electricity which unites 

 the elements of that grain of water together, and is equiva- 

 lent to the quantity of atmospheric electricity which is active 

 in a very powerful thunder-storm. These laws are universal, 

 and are of that high and general order that characterise all 

 great discoveries, andperfectly agree with Professor Mossotti's 

 theory. 



Dr. Faraday has given a singular instance of cohesive force 

 inducing chemical combination, by the following experiment, 

 which seems to be nearly allied to the discovery made by M. 

 Drebereiner, in 1823, of the spontaneous combustion of spongy 

 platina (N. 159) exposed to a stream of hydrogen gas mixed 

 with common air. A plate of platina with extremely clean 

 surfaces, when plunged into oxygen and hydrogen gas mixed 

 in the proportions which are found in the constitution of 

 water, causes the gases to combine and water to be formed, 

 the platina to become red-hot, and at last an explosion to take 

 place ; the only conditions necessary for this curious experi- 

 ment being excessive purity in the gases and in the surface 



