90 Mr. H. Wilde's Experimental Researches 



on the cylinder, the addition of a second magnet increased the 

 sustaining-power of the electro-magnet by 66*5 lbs., whereas 

 when three magnets were placed on the cylinder, the addition 

 of a fourth magnet was only attended by an increase of 28 lbs. 

 in its sustaining-power. 



32. But the most extraordinary fact brought out in connexion 

 with the latter series of experiments is the development of a 

 much greater amount of magnetism in the electromagnet than 

 that which existed in the permanent magnets employed in 

 exciting it; for while the four permanent magnets on the 

 cylinder were only capable, collectively, of sustaining a weight 

 of about 40 lbs., the electromagnet, as will be seen from the 

 Table, would sustain a weight of 178*5 lbs. 



33. In order that this remarkable property might be exhibited 

 in a more striking manner, a large electromagnet was con- 

 structed by screwing into a heavy iron block, 6 inches in thick- 

 ness, two cylinders of wrought iron 24 inches in length and 3 J 

 inches in diameter. Round each of these cylinders an insulated 

 strand of copper wires, each 950 feet in length and 0*15 of an 

 inch in diameter, was wound from end to end of the cylinders 

 in several concentric layers, and the two electron elices were 

 coupled up so as to form one continuous helix 1900 feet in 

 length. The cylindrical poles of the electromagnet were 8| 

 inches distant from centre to centre, and were furnished with a 

 suitable submagnet, which was connected by means of a link 

 with a strong lever, for the purpose of measuring the amount of 

 force necessary to separate the submagnet from the electro- 

 magnet. 



34. When the four permanent magnets (20) were placed on 

 the cylinder of the magneto-electric machine, and the electricity 

 from it was transmitted through the electromagnetic helices, 

 a weight of not less than 1088 lbs. was required to overcome 

 the attractive force of the electromagnet, or twenty-seven times 

 the weight which the four permanent magnets used in exciting- 

 it were collectively able to sustain. It will, however, be shown 

 hereafter (77) that this difference between the sustaining-power 

 of a permanent magnet and that of an electromagnet excited 

 through its agency, great as it is, is very far from reaching the 

 limits to which it can be carried. 



35. The question now arose, how the results obtained from 

 these experiments were to be reconciled with the principle of 

 the conservation of force, since it is now generally held by 

 physicists that the calorific, magnetic, and other properties of 

 the electric circuit are correlated, both in diretion and amount ; 

 and to admit the coexistence of any one of these properties 

 along with the others in a greater or less degree, under like 



