110 ANNUAL OF SCIENTIFIC DISCOVERY. 



electro-magnets in six frames and ten movable wheels making the 

 contacts has given a power of fifty-five kilogrammes per second. 

 M. De la Rive, however, does not think that electro-motive machines 

 can be ever profitably employed in industrial pursuits, but points out 

 their advantage in regard to their avoiding the dangers of fire and 

 explosion, as in the case of steam, and in requiring only a voltaic bat- 

 tery to put them in action. 



MAGNETIC PHENOMENA. 



M. Ruhmkorffhas the following notice in the Comptes-Rendus, vol. 

 1, p. 166 : " If a stay (bride) of soft iron be pressed against one of 

 the poles of an artificial magnet, the soft iron is observed to become 

 hard, and it is more difficult to file. If the stay be removed, it loses 

 its hardness and resumes all the properties of soft iron." 



NEW THEORY OF MAGNETIC CURRENTS. 



Prof. Challis of Cambridge, England, has put forth the theory that 

 magnetic currents are induced in the mass of the earth by its rota- 

 tion. These currents, he says, are subject to modification by the 

 earth's movement of translation, and also by the want of perfect sym- 

 metry in form. These deviations from symmetry determine the direc- 

 tion of the magnetic streams, which appear from experiment to enter 

 the earth on the north side of the magnetic equator and to issue from 

 it on the south side. The earth is thus a vast magnet, the streams of 

 which are of constant intensity, excepting so far as they may be dis- 

 turbed by cosmical influence. In this matter the sun and each of the 

 planets act their part. That of Jupiter is likely to be predominant 

 on account of his large size and rapid rotatory motion, and the Pro- 

 fessor says it is not a little singular that the periodic time of Jupiter 

 should coincide with the magnetic period discovered by General Sa- 

 bine. This period has been shown in this country to be the same as 

 that of the waxing and waning of the sun's spots ; and it may very 

 well be that the three are produced by the same cause. 



MAGNETIC DISTURBANCES CAUSED BY THE MOON. 



Prof. Airy, at the British Association, 1861, in discussing the mag- 

 netic deviations apparently caused by the moon, gave as his opin- 

 ion, that they followed the law of the double tides, having the same 

 epochs. There was a double tide of magnetism every lunar day, fol- 

 lowing the hours like the tides. There was, however, a considerable 

 discordance in the results obtained for the several vears of observation, 



* 



though this did not destroy their value. No action of the moon as an 

 independent magnet could produce this, and probably the influence 

 was a reflected one from the magnetic earth. He also su^crested that 



CJ ^^J 



it was probable that the moon produced a double tide in the air, and 

 if so in the oxygenic part of it. and they were therefore justified, from 

 the recent discoveries of Mr. Faraday, in expecting a magnetic dis- 

 turbance twice a dav. 



