150 Royal Society : — 



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 analogous to, but not identical with, that 

 in which it is retained in insulated 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 permanent 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 con- 

 sideration of these experiments is, that when an electro-magnet is 

 excited through the agency of a permanent magnet, the large amount 

 of magnetism manifested in the electro-magnet, simultaneously with 

 the small amount manifested in the permanent magnet, is the con- 

 stant 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 accu- 

 mulating and retaining a temporary charge of electricity, or of mag- 

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

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

 nomena 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 proportionately large amount of dynamic 

 electricity. 



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

 inches, and a length of 1 2-|- inches or five times the diameter of the 

 bore. 



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

 ployed 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 67 feet in length, and O'lo of an 

 inch in diameter. Upon one of the magnet-cylinders sixteen per- 

 manent 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 equal velocity of 2500 

 revolutions per minute. When the electricity from the magneto- 

 electric machine was transmitted through a piece of No. 20 iron 

 wire 0*04 of an inch in diameter, a length of 3 inches of this wire 

 was made red-hot. When the direct current from the magneto-elec- 

 tric machine was transmitted through the coils of the electro-mag- 



