Electro-magnetic Experiments. 407 



of greater weight would have lifted more; perhaps ihe gun harrel 

 was not sufficiently thick for the full developement of magnetism, 

 which, according to Barlow's experiments, resides near the surface. 



A series of experiments! were separately instituted by Dr. Ten 

 Eyck in order to determine the maximum developement of magnetism 

 in a small quantity of soft iron ; from these the following interesting 



results were obtained. 



Experiment 1. A horse-shoe of round iron -^% of an inch in di- 

 ameter, 4 inches long, weighing 2314 grains and wound with 23 it. 

 copper-wire diameter T £|„ of an inch, with a pair of one inch plates, 

 lifted 19 lbs. 5oz. Cdwt. 16 grs. ; with a pair of 4 inch plates, lifted 

 251bs. 6oz. 5dwt. ; with the cylindrical element used in E.\|»s. 8, 

 and 10 of former series, it lifted 42 lbs. 6 oz. 8 dwt. 8 grs., or 106 times 



its own weight. 



Exp. 2. A horse-shoe of round iron \ inch in diameter, 3£ inches 



in length weighing 310 grains, and wound with 15 ft. copper wire, di- 

 ameter T A§ 7 inch, with a pair of one inch plates, lifted 3 lbs. 11 oz. 

 7 dwt. 22 grs. ; with 4 inch plates it lifted 5 lbs. 5 oz. 12 dwt. 12 grs.; 

 with the cylindrical element 8 lbs. 2 oz. 8 dwt. 18 grs., or 152 times 



its own weight. 



Exp. 3. A horse-shoe formed of a flat bar 2^ inches long ft 

 broad and T f thick, weighing 84 grains, and wound with 16 ft. of 

 brass wire, T f of an inch in diameter, with a pair of one inch plates, 

 lifted 5 lbs. 2oz. 3 dwt. 8 grs. ; with 4 inch plates, lifted 2 Ibs.jlOoz. 

 2 dwt. 12 grs. ; with the cylindrical element 2 Ibs.lOoz. 13 dwt. 2 



grs., or 198 times its own weight. 



Exp. 4. A horse-shoe of round iron slightly flattened, one inch in 

 length, diameter, (before flattening) T f inch, weight 6 grains and 

 wound with 3 feet brass wire same diameter as that of No. 3. with a 

 pair of one inch plates, lifted 2 oz. 15 d. 1 gr. ; with four inch plates, lift- 

 ed 3 oz. 17 dwt. 10 gr.; with the cylindrical element 5 oz. 5 dwt. 1 



rrs., or 420 times its own weight. 



In this last result the ratio of the weight lifted, to the weight of the 

 magnet is much greater than any we have ever seen noticed : the 

 strongest mairnet we can find described is one worn by Sir Isaac New- 



■S""" *""fa 



ton in a ring, weighing 3 grains, it is said to have taken up 746 grs. or 



nearly 250 times its own weight. M. Cavallo has seen one of 6 or 7 

 grs. weight which was capable of lifting 300 grs. or about 50 times 

 its own weight. From these experiments it is evident, that a much 

 greater degree of magnetism can be developed in soft iron by a gal- 

 vanic current, than in steel by the ordinary method of touching. 



Most of the results given in this paper, were witnessed by Dr. L. 

 C. Beck, and to this gentleman we are indebted for several sugges- 



*^^^"' " >'■■■■ ,.,,■—■» — — " ' ■■ ■ ■■ 1 > ■ ■ 



* See Barlow's Essay on Magnetic attractions, page 50, 

 t Troy weight U used in these experiments. 



