74 Electro-magnetic Experiments. 



tance of the needle centre from that of the neighbouring pole 

 was 10 feet, and the strength of the acid charges was varied. 



1st charge, 1 of acid to 40 of water, deflection . . 2 15 



2d do. 1 of acid to 20 of water, do. . . 3 30 



3d do. 1 of acid to 10 of water, do. . . 4 12 



4th do. 1 of acid to 5 of water, do. . . 4 16 

 With this last charge still in, the' distance was increased 



to 1 1 feet, when deflection decreased to . . 3 46 



to 12 feet, do. do. . . 2 



to 13 feet, do. do. . . 1 15 



■ .. to 14 feet, do. do. . . 1 



There will be observed a great disproportion between the re- 

 sults of the first of these latter experiments and the last of the 

 former ; this the operator can only attribute to the difference 

 between the times at which the two observations were taken ; 

 the former having been taken some time after the battery had 

 exerted its full energy, and the latter immediately after the bat- 

 tery was charged, and while it was in its highest state of activity. 

 Lastly, three of the batteries were taken and charged, Ist^ two 

 together connected as one pair ; 9.(1^ the three together as one 

 pair; and, 3c?, the three as a series of three pairs ; and it was 

 observed that the effect produced was precisely the same as if 

 only one pair had been employed with a charge of the same 

 strength. Each pair consists, it should have been stated, of one 

 plate of zinc, 1 foot square, opposed by one similar surface of 

 copper. 



The operator has not had any means of testing fully the 

 suspension powers of the electro-magnet ; of its enormous coer- 

 cive power, however, he can give a striking example. A steel- 

 bar (of cast-steel), bent into the horse-shoe form, and weighing 

 321b., was passed once over the poles of the electro-magnet, 

 while excited by a battery charged with 1 of acid to 12 of wa- 

 ter, and immediately the steel supported itself with ease from a 

 piece of soft iron. In order to render the above experiments 

 more complete, an attempt was tnade to ascertain the degree in 

 which each successive thickness of wire contributed to the sum 

 of magnetic influence excited by all together ; but it was found 

 that the partial contact which the method of construction adopt- 

 ed allows of among the wires of the same tier, before they enter 

 the insulating envelopes, interfered with the experiments ; for, 

 when one wire only was introduced into the galvanic circle, it 

 communicated the galvanic fluid to all the other members of the 



