Mr. H. Wilde's Researches in Magnetism and Electricity, 14-9 



ings, and to some of those maxims which philosophers propound 

 for the consideration of others. 



The author directs attention to some new and paradoxical pheno- 

 mena arising out of Faraday's important discovery of magneto- 

 electric induction, the close consideration of which has resulted in 

 the discovery of a means of producing dynamic electricity in quantities 

 unattainable by any apparatus hitherto constructed. He has found 

 that an indefinitely small amount of magnetism, or of dynamic elec- 

 tricity, is capable of inducing an indefinitely large amount of magne- 

 tism, — and again, that an indefinitely small amount of dynamic 

 electricity, or of magnetism, is capable of evolving an indefinitely 

 large amount of dynamic electricity. 



The apparatus with which the experiments were made consisted 

 of a compound hollow cylinder of brass and iron, termed by the 

 author a magnet-cylinder, the internal diameter of which was 11- 

 inch. On this cylinder could be placed, at pleasure, one or more 

 permanent horseshoe magnets. Each of these permanent magnets 

 weighed about 1 lb., and would sustain a weight of about 10 lbs. 

 An armature was made to revolve rapidly in the interior of the cylin- 

 der, in close proximity to its sides, but without touching. Around 

 this armature 163 feet of insulated copper wire was coiled, 0'03 

 of an inch in diameter, and the free ends of the wire were connected 

 with a commutator fixed upon the armature-axis, for the purpose 

 of taking the alternating waves of electricity from the machine in 

 one direction only. The direct current of electricity was then trans- 

 mitted through the coils of a tangent galvanometer ; and as each addi- 

 tional magnet was placed upon the magnet-cylinder, it was found 

 that the quantity of electricity generated in the coils of the armature 

 was very nearly in direct proportion to the number of magnets on 

 the cylinder. 



Experiments were then made for the purpose of ascertaining what 

 relation existed between the sustaining-power of the permanent mag- 

 nets of the magnet-cylinder, and that of an electro-magnet excited 

 by the electricity derived from the armature. 



When four permanent magnets capable of sustaining collectively a 

 weight of 40 lbs. were placed upon the cylinder, and when the sub- 

 magnet was placed in metallic contact with the poles of the elec- 

 tro-magnet, a weight of 178 lbs. was required to separate them. 

 With a larger electro-magnet a weight of not less than 1080 lbs. 

 was required to overcome the attractive force of the electro-magnet, 

 or twenty-seven times the weight which the four permanent magnets 

 used in exciting it were collectively able to sustain. It was further 

 found that this great difference between the power of a permanent 

 magnet and that of an electro-magnet excited through its agency 

 might be indefinitely increased. 



Experiments were then made with electro-magnets of various sizes, 

 for the purpose of ascertaining the cause of these paradoxical results. 



When thfi wires forming the polar terminals of the magneto- 

 electric machine were connected for a short time with those of a very 

 large electro-magnet, a bright spark could be obtained from the 

 electro-helices twenty-five seconds after all connexion with the magneto- 



