Electro-magnetic Experiments. 407 



of greater weight would have lifted more ; perhaps the gun barrel 

 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 y\% of an inch in di- 

 ameter, 4 inches long, Aveighing 2314 grains and wound with 23 ft. 

 copper-wire diameter y||o of an inch, with a pair of one inch plates, 

 lifted 19 lbs. 5oz. 6dwt. 16 grs. ; with a pair of 4 inch plates, lifted 

 251bs. 6 oz. 5 dwt. ; with the cylindrical element used in Exps. 8, 9 

 and 10 of former series, it lifted 42 lbs. 6 oz. 8 dwt. 8 grs., or 105 times 

 its own weight, 



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

 in length weighing 310 grains, and Avound Avith 15-ft, copper wire, di- 

 ameter yf f 0- inch, Avith 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 OAvn Aveight. 



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

 broad and yf^ thick, Aveighing 84 grains, and wound with 16 ft. of 

 brass Avire, yf „ of an inch in diameter, Avith a pair of one inch plates, 

 lifted 5 lbs. 2oz. 3 dAvt. 8 grs. ; Avith 4 inch plates, lifted 21bs.|10oz. 

 2 dwt. 12 grs. ; Avith the cylindrical element 2 lbs . 10 oz. 13 dAvt. 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) y|j inch, Aveight 6 grains and 

 Avound Avith 3 feet brass Avire same diameter as that of No. 3. Avith a 

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

 ed 3 oz, 17 dwt, 10 gr. ; with the cylindrical element 5 oz. 5 dwt. 4 

 grs., or 420 times its OAvn Aveight. 



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

 magnet is much greater than any Ave have ever seen noticed ; the 

 strongest magnet we can find described is one Avorn by Sir Isaac New- 

 ton in a ring, Aveighing 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. Aveight Avhich was capable of lifting 300 grs. or about 50 times 

 its OAvn Aveight. 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, Avere Avitnessed by Dr. L. 

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



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

 t Troy weight \% usedyin these experiments. 



