568 Proceedings of the 



miasma may emanate. We should mention that these opinions of 

 Dr. Jahinichen have been warmly attacked by M. Moreau de Johnes, 

 and other advocates of the contagious properties of the disease, but 

 their arguments are rather theoretical than founded on specific facts. 



NATURAL PHILOSOPHY. 



Electrical relations of bodies to heat. At the meeting of the 

 Acad6mie des Sciences, held on the 17th of January, M. Becqueril 

 read a memoir entitled * Theoretical considerations on the changes 

 operated in the electrical state of bodies, by the action of heat, con- 

 tact, friction, and different chemical actions, and on the modifica- 

 tions which are occasionally produced in the arrangement of the 

 constituent parts of those bodies.' The object of this memoir is to 

 explain some of the causes which in process of time effect a change 

 in many of the substances forming, the superficial stratum of the 

 globe. After referring to Laplace's theory of the igneous origin of 

 the earth, he observes, that the diminution of the temperature must 

 have successively produced great change in the combination of the 

 elements of which the bulk of the earth is composed, in the con- 

 stitution and pressure of the atmosphere, &c. He proposes to trace 

 the origin of all these phenomena, and to investigate their causes 

 and physical laws, and commences by some general considerations 

 on certain properties of matter ? after which he examines the effects 

 of heat on the electric fluid of metallic substances considered sepa- 

 rately and in contact, and the state of the atoms in the various 

 combinations. By means of a very simple apparatus, he demon- 

 strates that heat does not possess any influence over free elec- 

 tricity ; but on the contrary acts very decidedly on the natural 

 fluid. He has observed, that, the heat which separates the mole- 

 cules of bodies, produces on the natural fluid an effect analogous 

 to that obtained by the cleavage of regularly crystallized substances, 

 viz. the diminution of the reciprocal action of the two electricities. 

 He then enumerates a variety of experiments, which authorize the 

 conclusion, that the two electricities are raised by heat to a higher 

 degree in bodies which are negatively than in those which are 

 positively electric. This fact explains the reason of the oxides of 

 the negatively electric metals being more easily decomposed by heat 

 than those of other metals. He then, after having given a detailed 

 account of the various phenomena relating to the influence of heat 

 in exciting the electric power in metals, enters into the question of 

 the development of electricity by contact. Volta, in attacking 

 Galvani's theory on muscular contractions, conceived the idea that 

 they were owing to the electricity emanating from the contact of 

 two heterogeneous substances : according to his theory, two sub- 

 stances always become in a state of contrary electricity by mutual 

 contact, leaving out of consideration any modifications produced on 

 the surfaces in contact. M. Becqueril then noticed the theory, 



