94 
ME. H. WILDE’S EXPERIMENTAL EESEAECHES 
exactly counterbalance the weight of the submagnet. The stand supporting the scale- 
beam was firmly bolted to an iron lathe-bed, as was also the electro-magnet, which was 
placed in a vertical position beneath the submagnet. 
28. Around each side or plate of the electro-magnet, a length of 100 feet of insulated 
copper wire 0-05 of an inch in diameter was coiled, and the ends of the wires were so 
arranged that they could, at pleasure, be coupled up so as to form a single circuit of 200 
feet, or a double circuit of 100 feet in length. One foot of the wire on the armature of 
the magneto-electric machine had a resistance equal to 3 feet of the single wire on the 
electro-magnet. 
24. Experiments Were made, in the first instance, for the purpose of ascertaining what 
influence the number of magnets on the magnet-cylinder had upon the attractive force 
mutually exerted by the electro-magnet and the submagnet. As the scale-beam was of 
too delicate a construction to allow of the submagnet being placed in direct metallic 
contact with the electro-magnet, a piece of thin cardboard was fastened upon the poles, 
by means of gum. The wires of the electro-magnet were coupled up so as to form a 
double circuit 100 feet in length, the resistance of which was about one-tenth of the 
resistance of the armature circuit. The electro-magnet was excited by the direct current 
from the magneto-electric machine. The submagnet was then placed upon the covered 
poles of the electro-magnet, and small weights were introduced into the scale-pan of the 
balance until the submagnet was separated from the electro-magnet. 
25. In order that a more rigid comparison might be made between the quantities of 
electricity derived from the magneto-electric machine and the amount of the attractive 
force mutually exerted by the electro-magnet and the submagnet, the particular expe- 
riments, the results of which are given in Tables I. and II., were made simultaneously, 
the tangent galvanometer at the same time forming pafit of the same metallic circuit 
as the electro-helices and the wire surrounding the armature. 
26. Coordinate results, such as are shown in Tables I. and II., were, however, obtained, 
whether the first and second series of experiments were made either together or sepa- 
rately. 
Table II. 
No. of magnets on cylinder. 
Weight, in ounces, required to separate 
submagnet from electro-magnet. 
Squares of magnetic force of 
the magnet-cylinder. 
1 
2-50 
2-50 
2 
11-25 
10-00 
3 
24-00 
22-50 
4 
38-00 
40-00 
27. The results arrived at, as shown in the above Table, are somewhat remarkable, 
and have amongst themselves a well-defined ratio, such as would hardly have been 
expected from a bare consideration of the nature of the magnetism of the permanent 
magnet ; for when one magnet was placed on the cylinder, the weight required to sepa- 
rate the submagnet from the electro-magnet was 2 ‘5 ozs. It might therefore have been 
