182 Miscellaneous Intelligence. 



precious metals. This is a convenient mode of testing the purity 

 of mercury. Dr. Hare observed, that when the poles of the excited 

 galvanic magnet are brought into contact with the mercury, commu- 

 nicating with one pole of the calorimeter, the vertex of the magnet 

 being in contact with the other pole, a gyratory or whirling motion 

 may be observed in the mercury *. The effect is identical with the 

 vortices of Davy, or the rotation of Faraday. 



3. POWERFUL ELECTRO-MAGNET. (By Professor Henry and Dr. 



Ten Eyck.) 



In the last number of this Journal, page 609, we gave an account 

 of a powerful electro-magnet, constructed in America, by Professor 

 Henry and Dr. Ten Eyck, which was capable of sustaining about 

 750 Ibs. These gentlemen have carried their researches still 

 further, and have actually constructed an electro-magnet for Yale 

 College, which is said to have sustained 2063 Ibs., or nearly a ton ! 

 It was constructed on the same principle as the former, but a greater 

 number of strands of copper wire were employed. ' The magnet is 

 wound with 26 strands of copper bell-wire, covered with cotton 

 thread, 31 feet long; about 18 inches of the ends are left project- 

 ing, so that only 28 feet of each actually surround the iron ; the 

 aggregate length of the coils is, therefore, 728 feet. Each strand is 

 wound on a little less than an inch ; in the middle of the horseshoe 

 it forms three thicknesses of wire, and on the ends or near the poles, 

 it is wound so as to form six thicknesses.' With a battery of 4-J 

 square feet, the magnet suspended 2063 Ibs. The effects of a larger 

 battery were not tried. It induced magnetism in a piece of soft 

 iron, so energetically, as to raise 155 Ibs. When two batteries were 

 employed so that the poles could be rapidly reversed, a curious fact 

 was observed. After one of the batteries had been removed, the 

 armature, with a weight added, in all 89 Ibs., remained sus- 

 pended, and did not fall when the poles were reversed. This effect 

 must have been instantaneous, otherwise the weight must have 

 fallen, as there was an instant when the magnet could have had no 

 power. It was attempted to decompose water by this magnet, but 

 without success |- 



4. ON ELECTRICITY INDUCED BY THE RED AND VIOLET RAYS OP 



THE SOLAR SPECTRUM. 



Professor Saverio Barlocci, of Rome, states that when two pieces of 

 copper, painted black, and one of them connected with the upper part 

 of a frog, and the other with the hind feet, are placed one of them in 

 the red, and the other in the violet ray of the solar spectrum, and then 



* Sillnnan's Journal, xx., page 143. f Id. xx., page 201. 



