Electricity — Galvanism. 179 



In M. (Pouillet's Memoir, he speaks of the large compound lenses 

 as " la belle invention de M. Fresnel." M. Pouillet ought to have known 

 that they were invented long before in Scotland. 



16- Electricity of the Atmosphere. — M. Pouillet has shown that electri- 

 city is developed during the vegetation of plants, shewing itself the moment 

 thut the germ appears above ground. He, therefore, concludes that this 

 is a fertile source of atmospherical electricity. — Id. May, p. 69. 



17. Electricity of Flame. — M. Pouillet has shown that, in a vertical 

 flame formed by the combination of hydrogen with oxygen, the visible 

 part of the flame, and the part without it, to the distance of a centimetre, 

 is positively electrified, while, in the interior of the flame, resinous elec- 

 tricity alone is found. Id. 



18. Subterraneous Passage of Lightning-. — On the 28th May 1824, a 

 tree in Vernon, Connecticut, was struck with lightning. After passing 

 down the tree, and tearing up the earth at its root, the electric fluid pass- 

 ed " 50 or 80 feet under the surface of the earth without following any 

 such substances as commonly guides its course there, as roots, stones, &c. 

 The fluid seems not to have been guided at all by any attracting sub- 

 stance, but to have been carried forward nearly in a straight course by a 

 momentum it had received, through a medium opposing the most powerful 

 resistance, a medium in which it is commonly supposed to be dissipated 

 and lost." The electric fluid left unequivocal traces of its passage through 

 a distance of nearly 50 feet. Through the distance of other 30 feet there 

 can be no doubt of its having passed, as its effects upon a wall were dis- 

 tinct at that distance ; and it cannot be supposed that it came out of the 

 ground and leaped 30 feet to the wall. This account is given by Professor 

 Kellogg, in Professor Silliman's Journal, vol. ix. p. 84 — 86. 



GALVANISM. 



19. Analogy hctween the Phenomena of Galvanism and those of Fermen- 

 tation. — M. Schweigger has observed this analogy in the following points: 



1. Galvanic piles, like fermentable mixtures, exhibit their effects only 

 by the reciprocal action of three different bodies. 



2. The products of galvanic action are two, an oxidated body, and a 

 hydrogenatcd body. The same happens with the products of fermenta- 

 tion, which are alcohol and carbonic acid. 



3. The presence of electro-negative bodies favours the decomposition of 

 water, whilst, according to Dobereiner, electro-positive bodies determine 

 the formntion of it. 



M. Schweigger is of opinion, that the same results may be obtained 

 with fermentable mixtures, as with electrical batteries ; but several ex- 

 periments, made subsequently by M. Dobereiner, stand in opposition to 

 this hypothesis. Schweiggcr's Journal sur Phys. &c vol. x. call. 3d. 1824, 

 and vol. xi. call. 4, pt 457. 



