Mechanical Science. 403 



took anew, a work which this savant appeared to me to have com- 

 pleted with admirable sagacity ; nevertheless, the success of my 

 researches has exceeded what I could have hoped. I shall briefly 

 state the method which I followed, and the causes which may 

 prevent the magnetization which it is the object to produce. 



As for the method, I introduce into a dark room a solar ray, by 

 means of an heliostat, and decompose it, so that the spectrum is 

 formed horizontally ; I then place under the violet ray, in a direc- 

 tion perpendicular to that of the magnetic meridian, the extremity 

 only of the wire that I wish to magnetize. In this way I obtained 

 the following results : — 



i. Having placed in the above position a wire of soft iron highly 

 polished, four inches in length, and a quarter of a line in diameter, 

 at the end of 5 minutes, I found that the extremity exposed to the 

 violet ray had acquired a north pole. At the end of 8 minutes, this 

 wire, presented to a magnetised needle, shewed very decidedly that 

 it had poles. 



ii. I exposed, in the same way, two wires of soft iron, similar to 

 the preceding, to the action of white light ; at the end of 5 minutes 

 each of the two exposed extremities had acquired a north pole; but 

 it was weak, and at the end of a tew minutes had disappeared. In the 

 first case, as in the present one, I ascertained, carefully, that the 

 wires employed did not previously possess any sensible magnetism, 

 iii. The violet ray reversed the very decided poles of a wire of 

 soft iron ; it developed, very distinctly, in 6 or 7 minutes, those of 

 another wire, which evinced at its two extremities a very feeble 

 repulsion for the pole of a needle. 



iv. Having placed one extremity of a magnetized needle in the 

 red, orange, yellow and green rays, and having observed the nature 

 of its poles and their energy, at the end of 6 or 7 minutes I found 

 no alteration whatever ; neither did I remark any effect produced 

 by this operation on a needle which had no perceptible magnetism, 

 v. A soft iron wire, covered with a coat of rust, and strongly 

 magnetized, having been exposed to the violet ray, in 3 minutes 

 the south pole was converted into a north pole. 



vi. A wire of soft iron, highly polished and magnetized, having 

 been exposed by its two extremities to the violet ray, in 10 minutes 

 a north pole was formed at each of its ends. 



vii. If the iron wire be oxidized, the same effect takes place in 5 

 minutes. 



The dimensions of all the wires employed was uniformly the 

 same as those of the one that has been mentioned. All these ex- 

 periments, which, repeated several times, invariably gave the same 

 results, have placed beyond doubt the magnetizing property of the 

 violet ray ; but I must add, that in performing them I have encoun- 

 tered innumerable difficulties, which have clearly shewn to me the 

 causes of the bad success of the attempts of many philosophers. I 



