1831] WRITINGS OF JOSEPH HENRY. 45 



ishing result, it must bo remembered, was produced by a 

 battery containing only f of a square foot of zinc surface, 

 and requiring only half a pint of diluted acid for its sub- 

 mersion. 



Exp. 15. .4 small battery, formed with a plate of zinc 12 

 inches long and 6 inches wide, and surrounded by copper, was sub- 

 stituted for the galvanic element used in tlie last experiment; the 

 weight lifted in this case was 750 lbs. This is probably the 

 maximum of magnetic power which can be developed in 

 this horse-shoe, as with a large calorimotor, containing 28 

 plates of copper and zinc, each 8 inches square, the effect 

 was not increased, and indeed we could not succeed in mak- 

 ing it lift as much as with the small battery. 



The strongest magnet of which we have any account, is 

 that in the possession of Mr. Peale, of Philadelphia; this 

 weighs 53 lbs. and lifted 310 lbs. or about six times its own 

 weight. Our magnet weighs 21 lbs. and consequently lifts 

 more than thirty -five times its own weight ; it is probably, 

 therefore, the most powerful magnet ever constructed. 



This, however, is by no means the maximum, which can 

 be produced by a small galvanic element, as in every ex- 

 periment we have made the power increases by increasing 

 the quantity of iron ; with a bar similar to the one used in 

 these experiments, but of double the diameter, or of 8 times 

 the weight, the power would doubtless be quadruple, and 

 that too without increasing the size of the galvanic element. 



Exp. 16. In order to ascertain the effect of a very small gal- 

 vanic element on this large quantity of iron, a pair of plates, 

 exactly one inch square, was attached to all the wires; the weight 

 lifted was 85 lbs. 



The following experiments were made with wires of dif- 

 ferent lengths, on the same horse-shoe. 



Exp. 17. With 6 wires, each 30 feet long, attached to the 

 galvanic element, the weight lifted was 375 lbs. 



Exp. 18. The same wires used in the last experiment, were 

 united so as to form 3 coils of 60 feet each; the weight sup- 

 ported was 290 lbs. This result agrees nearly with that of 

 Exp. 11, though the same individual wires were not used; 



