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ON ELECTRICITY, AND ON THE NATURAL SOURCES OF ELECTRI- 

 CITY AND MAGNETISM. Bl/ ProfeSSOV M, A. DE la JRiVE. 



I. Atmospheric and Animal Electricity, 

 Concerning atmospheric electricity, the beautiful work in 

 the Memoires de TAcademie des Sciences, upon lightning con- 

 ductors, ought not to be overlooked. This memoir *, drawn up 

 by M. Gay Lussac, is composed of two distinct parts. In the 

 former, he furnishes a very lucid and complete summary of the 

 theory of thunder and conductors. He briefly recapitulates the 

 electrical phenomena upon which this theory is founded, and the 

 results which observation and experience have afforded on the 

 subject. He dwells upon the dangers of imperfect conductors, 

 and of such as are interrupted, or not sufficiently large to resist 

 the heating influence of the lightning. He also insists upon 

 the necessity of their having as free an entrance as possible into 

 the soil beneath. In accordance with the opinion of M. Charles, 

 who attended a great deal to this subject, he believes that a con- 

 ductor will thoroughly protect from the assaults of lightning, a 

 circular space having a radius of a length double the height of 

 the conductor ; a rule, according to which buildings ought to be 

 protected. He finally cites a great many instances in which ac- 

 cidents have occurred from inattention to these precautions, or 

 from a total want of a conductor. He alludes to a remarkable 

 fact, which seems to prove that movement of the air facilitates 

 the descent of the thunderbolt, viz., that, in 1718, in the night 

 between the 14th and 15th of April, four-and-twenty church 

 towers, in all of which the bells were rung, were struck with 

 lightning in Brittany; whilst those escaped in which the bells 

 were not rung. He protests then strongly against the prevailing 

 |)ractice, especially in villages, of ringing the bells on the ap- 

 proach of a storm, with the purpose, it is alleged, of dissipating 

 and breaking up the thunder cloud. 



The practical part of the memoir includes a great number of 

 interesting details upon the construction of conductors. It is in 

 particular recommended, that the vertical rod shall be 28 or 30 

 feet high, of a pyramidal form, with a base of 2 inches on each 

 side, and, to prevent the oxidation of the iron, that it should 

 • Vide Ann. de Chim. et de Phys. t. xxvi. p. 258. 



