1866.] Mr. Wilde — Researches in Magnetism and Electricity. 109 



When the wn*es 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-electric machine had 

 been broken. Hence it is inferred that an electro-magnet possesses the 

 power of accumulating and retaining a charge of electricity in a manner 

 analog-ous to, but not identical with, that in which it is retained in in- 

 sulated submarine cables, and in the Leyden jar. It was also found that 

 the electro-helices offered a temporary resistance to the passage of the 

 current from the magneto-electric machine. When four magnets were 

 placed on the cylinder, the current from the machine did not attain a per- 

 manent degree of intensity until an interval of fifteen seconds had elapsed ; 

 but when a more powerful machine was used for exciting the electro- 

 helices, the current attained a permanent degree of intensity after an 

 interval of four seconds had elapsed. 



The general conclusion which is drawn by the author from a considera- 

 tion of these experiments is, that when an electro-magnet is excited through 

 the agency of a permanent magnet, the large amount of m.agnetism mani- 

 fested in the electro-magnet, simultaneously with the small amount mani- 

 fested in the permanent magnet, is the constant accompaniment of a 

 correlative amount of electricity evolved from the magneto-electric machine, 

 either all at once, in a large quantity, or by a continuous succession of 

 small quantities, — the power which the metals (but more particularly iron) 

 possess of accumulating and retaining a temporary charge of electricity, or 

 of magnetism, or of both together (according to the mode in which these 

 forces are viewed by physicists), giving rise to the paradoxical phenomena 

 which form the subject of this part of the investigation. 



Having established the fact that a large amount of magnetism can be 

 developed in an electro-magnet by means of a permanent magnet of much 

 smaller power, it appeared reasonable to the author to suppose that a large 

 electro-magnet excited by means of a small magneto-electric machine 

 could, by suitable arrangements, be made instrumental in evolving a pro- 

 portionately large amount of dynamic electricity. 



Two magnet-cylinders were therefore made, having a bore of 2^ inches, 

 and a length of 1 21 inches or five times the diameter of the bore. 



As frequent mention is made of the different-sized machines employed 

 in these investigations, they are distinguished by the calibre, or bore of the 

 magnet-cylinders. 



Each cylinder was fitted with an armature, round which was coiled an 

 insulated strand of copper wire 6/ feet in length, and 0'1.5 of an inch in 

 diameter. Upon one of the magnet-cylinders sixteen permanent magnets 

 were fixed, and to the sides of the other magnet-cylinder was bolted an electro- 

 magnet formed of two rectangular pieces of boiler-plate enveloped with 

 * coils of insulated copper wire. The armatures of the 2^-inch magneto- 

 electric and electro-magnetic machines were driven simultaneously at an 



