NATURAL PHILOSOPHY. 129 



tion, such as would be liable to arise from the fracture of the wire, it 

 is proposed to stretch two or three lines across the Channel, in differ- 

 ent places, at such distances from each other as to render it improb- 

 able that all would be broken the same day. In the event of one 

 being fractured, a repair could be easily effected hi a short time, by 

 means of steamers, kept continually in readines-s on both sides of the 

 Channel, for fishing up and discovering the broken wire. The im- 

 mense business of a line of telegraph between London and Paris 

 would, it is thought, justify a much greater expense than is involved 

 in the arrangement indicated. English Paper. 



DISCOVERIES IN MAGNETISM. 



BEETIN, in an examination of the rotation of the plane of polariza- 

 tion by the electro-magnet, or the wire helix, has been the first to 

 establish, under various circumstances, the law, that the rotation is 

 always in the direction of the magnetizing current, or of the currents 

 which, according to Ampere, would be set up, under the influence of 

 the electro-magnet, in a piece of soft iron, placed in the position of 

 the substance employed. 



It was considered, till lately, as an established fact, that the mag- 

 netism of steel magnets was entirely destroyed by a white heat, and 

 that at this temperature even iron no longer obeyed the attraction of 

 the magnet. Pouillet, indeed, had stated that cobalt remained mag- 

 netic even at a very high temperature, but that, on the contrary, the 

 magnetism of chromium disappeared at a heat somewhat below red- 

 ness, and that of nickel at 350. Recently, however, Faraday has 

 found by experiments with powerful electro-magnets, that even white- 

 hot iron, and nickel heated far above 350, still followed the attrac- 

 tion ; and Pliicker has more closely examined the behaviour of the 

 magnetic and diamagnetic properties under increasing temperature. 



Faraday considered that it might be concluded from his experi- 

 ments, that by an appropriate mixture of magnetic and diamagnetic 

 substances, a perfectly neutral body might be produced ; Pliicker, 

 however, has been led by his observations to an opposite conclusion. 

 The latter concludes, from a variety of experiments, that the diamag- 

 netism increases more rapidly than the magnetism, with an increasing 

 power in the electro-magnet ; and he considers it to be quite indiffer- 

 ent whether the increase of the intensity arises from the employment 

 of a greater number of cells, or from a closer approximation to the 

 poles. If these results are perfectly accurate, no absolutely neutral 

 body can exist ; for a body which behaves as neutral at any given 

 distance will be magnetic at a greater, diamagnetic at a less distance. 

 Liebig's Annual Report. 



ACTION OF MAGNETISM ON ALL BODIES. 



AT the meeting of the Paris Academy of Sciences, on May 

 21st, M. Edmond Becquerel communicated a paper upon the effects 

 of magnetism upon all bodies. The following are his deductions : 



