48 WRITINGS OF JOSEPH HENRY. [1831 



with 4 inch plates, it lifted 2 lbs. 10 oz. 2 dwt. 12 grs.; with 

 the cylindrical element, it lifted 2 lbs. 10 oz. 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) yf^ 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 dwt. 

 1 gr.; with four inch plates, lifted 3 oz. 17 dwt. 10 gr.; with 

 the cylindrical element, lifted 5 oz. 5 dwt. 4 grs., 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 magnet we can find de- 

 scribed is one worn by Sir Isaac Newton in a ring, weigh- 

 ing 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 evi- 

 dent, that a much greater degree of magnetism can be de- 

 veloped in soft iron by a galvanic 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 suggestions, and particularly that of substituting 

 cotton well waxed for silk thread, which in these investiga- 

 tions, became a very considerable item of expense; he also 

 made a number of experiments with iron bonnet-wire, 

 which, being found in commerce already wound, might pos- 

 sibly be substituted in place of copper: — the result was that 

 with very short wire the effect was nearly the same as with 

 copper, but in coils of long wire with a small galvanic ele- 

 ment, it was not found to answer. Dr. Beck also constructed 

 a horse-shoe of round iron, one inch in diameter, with four 

 coils on the plan before described ; with one wire it lifted 30 

 lbs., with two wires — 60 lbs., with three wires — 85 lbs., and 

 with four wires — 112 lbs. 



While we were engaged in these investigations, the last No. 

 of the Edinburgh Journal of Science was received, containing 



