196 Miscellaneous Intelligence, 



rapid exhaustion was effected j in 6 or 7 seconds the needle had 

 risen from 45.5 to 59 j it then became stationary for a moment, and 

 afterwards proceeded to indicate dryness with such rapidity, that 

 in 12 seconds the needle had traversed the circle. The exhaustion 

 being discontinued, and the air allowed to enter, it returned to the 

 point from whence it parted in 8 seconds, giving a motion over 

 105° in less than half a minute. — Recueil Industriel, xii. 45. 



6. Adhesion of Metals. — M. Prechtt states that the force with 

 which two plates of the same metal adhere, is the same as that 

 with which one of the plates will adhere to a plate of another metal, 

 having a less adhesion, however, for metal of its own nature ; 

 thus if two plates of copper will adhere with a force of 21 grains, 

 then one of these copper plates will adhere to a similar plate of 

 bismuth, zinc, tin, or lead, with the same force, although two 

 plates of any of these metals will adhere with a less force. — Bull. 

 Univ. A. xii. 440. 



7. Effect of Solar light upon Magnets. — This subject has been 

 investigated experimentally by M. Zantedeschi, with all the care 

 he could give to it, for the purpose of ascertaining, not the effect 

 of the decomposed and separated beam of light, or any particular 

 part of that beam, but the effect of the sun's light generally. 

 He has been, in part, anticipated by others ; but his results, if 

 exact, still add something to what was before known. The 

 scientific world is, however, now well aware, that numerous 

 influential causes, besides those which are purposely brought 

 into force, are frequently active, and that an unreserved assent 

 can hardly, as yet, be given to any of the statements which have 

 been made relative to the action of light, in producing and af- 

 fecting magnetism. 



M. Zantedeschi calls the phenomena electro-magnetic : if this 

 term is used in contradistinction to ordinary magnetism, we see 

 no reason for its use here ; for no reference is afterwards made to 

 any thing like electrical phenomena, or electrical conditions. 

 Barlocci has said that a magnet, able to carry lib. 6oz., after 

 being exposed for three hours to bright sun-light, raised 2oz. 

 more, and, in twenty-four hours, had its power doubled. A 

 similar magnet in a dark place remained unaltered; after two 

 days, the power did not increase. This and similar effects were 

 repeated and confirmed by M. Zantedeschi, who obtained the same 

 results with natural magnets. A dry, cloudy day produced no 

 effect of the kind. 



It appeared that magnets which were invested with a film of 

 oxide were thus strengthened by sun-light, but that those which 

 had been freed from oxide, on the contrary, became feebler, unless 

 the polish of the metal had been carried to such a degree, as to 

 enable it perfectly to reflect the sun's rays, and then no alteration 

 took place. 



