Scientific Intelligence. — Mechanical Philosophy. 175 



contained under a great number of pairs, to increase the intensity of 

 the phenomena which these different conductors are capable of de- 

 veloping. The chemical, calorific or luminous ejEFects, all those in 

 a word which are produced by imperfect conductors, will, [thereby, be 

 equal gainers. The two electric principles which are accumulated 

 at the two extremities of the pile and which are continually tending 

 to neutralize each other, have, in fact, two routes offered them for 

 this purpose, the one, the conductor which establishes the communi- 

 cation between the poles ; the other, the pile itself, v/hich is a hetero- 

 geneous and imperfect conductor, and the greater or less portion 

 of the electric current, which takes the one or the other of these 

 routes, will depend on their relative conductibility. If there be a 

 metallic wire, the pile may be reduced, even to a single pair, because 

 the current prefers the more perfect conductor ; but if the conductor 

 be jointed or heterogeneous, the conducting power of the pile itself 

 offers an approximate facility, and hence the difference must be in- 

 creased by an increase of number. But the necessity of reducing 

 the number of the elements of the pile in order to produce a great 

 effect in the case of a perfect conductor, can be accounted for, only 

 by distinguishing between intensity and swiftness. The first depends 

 on surface and number conjointly, the second principally on number, 

 because the current is the less retarded in passing through the pile, the 

 less the number of alternations of liquid and solid conductors. The 

 calorific effects of the pile, therefore in the case of a perfect conduc- 

 tor, can be sensible only when the swiftness is very great, and when, 

 from the construction of the pile this becomes reduced to a degree 

 inferior to that to which the resistance of the wire would reduce it, 

 there will be no development of heat, since this development pro- 

 ceeds from the effect of this resistance over the swiftness. 



It is true that by an augmentation of intensity the diminution of 



swiftness may be partially compensated : thus a pile of sixty pairs 



^ strongly charged may easily redden a wire ; but the ignition will not 



be so strong as with ten pairs only of the same pile. — Bib. Univ, 



Jan. 1829. 



4. Electro-magnetic property of carbon. — It appears from the ex- 

 periments of Mr. Kemp, [Edin. Phil. Journal, April, 1829.) that 

 coke and charcoal raised to the temperature of active combustion 

 and placed in the galvanic circuit, causes a wide deviation of the 

 magnetic needle. Very little effect is produced until the strips of 



