122 Astronomical and Nautical Collections, 



weight to the latter as accurate records of the transits of the Celes- 

 tial bodies ; and that they are noted for some subordinate pur- 

 poses only ; so that the transit instrument is the only authority that 

 bears on this question, 



vii. Second Memoir on the Theory of Magnetism. By Mr.' 

 PoissoN. Read to the Royal Academy of Sciences, 27th Dec. 

 1824. From the Annates de Chimie^ for January, 1825. 



The former memoir on this subject, which I read to the Academy 

 about a year ago, contains a detailed explanation of the principles 

 which form the basis of the application of mathematical analysis to 

 this important part of natural philosophy. These principles ar6 

 hypotheses, to which we are led by the consideration of the most ge- 

 neral facts in magnetism, and which are afterwards confirmed by the 

 comparison of the results of calculation with those of experiments. 

 The analogy which is observed between magnetic attraction and 

 repulsion, and the mutual actions of electrified bodies, inclines uS 

 at first to attribute these phenomena, in the case of magnetism as 

 well as in that of electricity, to two fluids, each of which attracts 

 the particles of the other, and repels with the same force its own 

 particles. But we soon discover that these imponderable fluids 

 cannot be disposed, in bodies capable of being affected by mag- 

 netism, as they are in bodies which conduct electricity. In the 

 latter, the two electrical fluids, as soon as they are separated from 

 each other, tend to escape at the surface, and may pass, in any 

 given quantity, from one body into another. But the case is dif-» 

 ferent with respect to the boreal and austral fluids ; for these fluids 

 never quit even the smallest bodies to which they belong, however 

 powerful the magnetizing forces may be : whence it has been in- 

 ferred, that within the substance of bodies that are magnetized, the 

 two magnetic fluids undergo displacements to an insensible dis- 

 tance only, which are nevertheless sufficient to render their action 

 sensible without the body, being repulsive for the one, and attrac- 

 tive for the other. 



I have given, in my former memoir, the name of magnetical elc" 



