INDUCTIVE AFFINITY. 



One reason for retaining the theory of an electr 

 fluids, is that it affords the means of expressing 

 terms those strictly physical laws, which are reputed ^^muui ; 

 and for many purposes such an hypothesis is unquestionably 

 useful, if not absolutely necessary ; but it has nothing to re- 

 commend it in the description of the chemical phenomena of 

 the voltaic circle. These admit of a perfectly intelligible 

 statement, when viewed as an exhibition of ordinary chemi- 

 cal affinity, acting in particular circumstances, without any 

 electrical hypothesis. It is often said that chemical affi- 

 nity acts only at insensible distances, and this may be true 

 of its direct action, but is not inconsistent with its exerting an 

 influence 'at a distance, like many other forces, by an inductive 

 agency, a mode of action which requires careful consideration. 



Magnetical polarity . The ideas of induction and polarity, 

 which now play so important a part in physical theories, were 

 originally suggested by the phenomena of magnetism, which 

 still afford the best illustrations of them. A bar magnet ex- 

 hibits attractive power which is not possessed in an equal 

 degree by every particle composing the bar, but is chiefly 

 localized in two points at or near its extremities. The powers, 

 too, residing at these points are not one and the same, or 

 similar, but different, indeed contrary in their nature ; and are 

 distinguished by the different names of Boreal magnetism and 

 Austral magnetism. The opposition in the mode of action of 

 these powers is so perfect, that they completely negative or 

 neutralize each other when residing in the same particle of 

 matter in equal quantity or degree, as they are supposed really 

 to exist in iron before it is magnetized ; and they only signalize 

 their presence when displaced and separated to a distance from 

 each other, as they are in a magnet. A body possessing any 

 such powers residing in it, which are not general, but local, 

 and not the same, but opposite, is said (in the most general 

 sense) to possess polarity. 



In the theory of magnetism, it is found necessary to con- 

 sider a magnet as composed of minute, indivisible particles or 



his Researches in the Philosophical Transactions for 1836, and the following 

 years, may be referred to. He has lately favoured the scientific world with a 

 reprint of the whole series : 'Faraday's Experimental Researches in Electricity, 

 R. and J. E. Taylor, London, 1839. The subject is als:> systematically treated 

 by Professor Daniell in his recent work, An Introduction to the Study of Chemi- 

 cal Philosophy, which may be consulted with advantage. 



