Electro-Magnetic Experiments. 333 



spiral was tried in its turn, but the precaution was taken of coating the 

 horse-shoe with silk. The iron spiral, wound to the left hand, was 

 three-sixteenths of an inch in diameter ; the weight of the apparatus 

 about three kilogrammes, or six pounds, the iron, connecting the 

 ends of the horse-shoe, about one and a quarter pound. The appa- 

 ratus thus arranged proved stronger than the former ; it supported 

 eighty-six pounds, or forty-three kilogrammes. 



Encouraged by these results, I increased the size of the hoise- 

 shoe, with a view of investigating whether any considerable augmen- 

 tation of power might be thus produced. I had a horse-shoe pre- 

 pared of about twelve and a half English inches high, and two and a 

 quarter inches in diameter. A brass spiral of one-eighth inch diam- 

 eter was wound forty-four turns from right to left round this strong 

 bar. The weight of the apparatus was about thirteen kilogrammes, 

 or twenty-six pounds. The connecting bar of the apparatus weigh- 

 ed about four pounds. With an acting galvanic surface of eleven 

 square English feet, the magnet supported sixty-seven kilogrammes, 

 or one hundred and thirty-five pounds weight. 



The horse-shoe was afterwards coated with silk, and an iron spiral 

 wire substituted for that of brass. The apparatus then supported one 

 hundred and jifty-f our pounds, but I could not succeed in making it 

 carry an anvil of two hundred pounds weight. 



It is well known that small magnets, generally speaking, are strong- 

 er in proportion to their size than larger ones. I procured a small 

 horse-shoe, coiled round with brass, and weighing in all two pounds. 

 It supported about six pounds. 



Vallemont* relates that S. Augustine, was considerably alarmed 

 and terrified, by witnessing some magnetic experiments, amongst 

 which was a magnet supporting several iron rings, suspended from 

 each other. The reverend father does not appear to have been 

 deeply read in Greek philosophers and Latin poets, else he might 

 have known, that the experiment which surprised him so much was 

 known in the days of Plato, and described by Lucretius. S. Au- 

 gustine would probably have been still more alarmed if he had seen 

 magnets capable of supporting one hundred and fifty-four pounds, 

 formed in an instant, and their poles taken away or altered with the 

 velocity of lightning. 



* Vallemont, Description de Vaimunt, qui s'en formf, a. la pointe du docker 

 neufde J\r. D. de Chartres, p. 164. 



Vol. XIX.— No. 2. 43 



