284 HENRY AND THE TELEGRAPH. 



ing different ends, the wLole may be formed into a double coil of half 

 the length, or into a triple-coil of one-third the length, &c. The horse- 

 shoe was suspended in a strong rectangular wooden-frame 3 feet 9 

 inches high and 20 inches wide." 



Two of the wires (one from each extremity of the legs) being joined 

 together by soldering, so as to form a single circuit of 120 feet, with its 

 extreme ends connected with the battery, produced a lifting-power of 

 60 pounds. (Experiment 19.) The same two wires being separately con- 

 nected with the same battery (forming a double circuit of 60 feet each), 

 a lifting-power of 200 pounds was obtained, (Experiment 10,) or more 

 than three times the power of the former case with the same wire. 

 Four wires (two from each extremity of the legs) being separately con- 

 nected with the battery (forming four circuits) gave a lifting-power of 

 500 pounds. (Experiment 12.) Six wires (three from each leg) united in 

 three pairs (forming three circuits of 180 feet each) gave a lifting-power 

 of 290 pounds. (Experiment 18.) The same six wires being separately 

 connected with the battery in six independent circuits, produced a lift- 

 ing-power of 570 pounds, (Experiment 13,) or very nearly double that of 

 the same wires in double-lengths. When all the nine wires were sepa- 

 rately attached to the battery a lifting-power of 050 pounds was evoked- 

 (Experiment 14.) In all these experiments " a small single battery was 

 used, consisting of two concentric copper cylinders, with zinc between 

 them ; the whole amount of zinc-surface exposed to the acid from both 

 sides of the zinc was two-fifths of a square foot ; the battery required 

 only half a pint of dilute acid for its submersion." 



" In order to ascertain the effect of a very small galvanic 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 pounds." (Experi- 

 ment 16.) For the purpose of obtaining the maximum attractive power 

 of this magnet, with its nine independent coils, " a small battery formetl 

 with a plate of zinc 12 inches long and 6 wide, and surrounded by cop- 

 per, was substituted for the galvanic element used in the former experi- 

 ments : the weight lifted in this case was 750 pounds." (Experiment 

 15.)* 



Although not directly connected with the purpose of this exposition, 



* Silliraan's Am. Jour. Sci. same vol. pp. 404, 405. The only European physicist wlw 

 at this period had obtained any magnetic results even approaching those eli'ected by 

 Henry, was Dr. Gerard Moll (professor of natural philosophy in the University of 

 Utrecht), who having- seen in England in 1828 an electro-magnet of Stm-geou's which 

 supported nine pounds (the very year in which Henry had exhibited a much more 

 powerful magnet before the Albany Institute), "determined to try the effect of a larger 

 galvanic apparatus" ; and in 1830 remarked, " I obtained results which appear astonish- 

 ing." Having formed a horse-shoe about twelve and a half iuches in height, of a round 

 bar of iron two and a quarter inches in diameter, he surrounded it with about 26 feet 

 of insulated ccpper wire one-eighth of an inch thick, in a tolerably close coil of 44 

 turns. The weight of the whole was about 26 pounds ; and with the curniit from a 

 galvanic pair of'about 11 square feet of zinc surface, the magnet sustained a weight of 

 154 pounds. (Brewsrer's Edinburgh Journal of Science, Oct., 183U, vol. iii, u. s. p. •214.) 

 Henry's magnet less in size and weight, lifted about live times this load, with only 

 one-eleventh of Moll's battery surface. 



