94 Proceedings. 



supplied, like gas and water, by the Corporation of the 

 City of Manchester. 



" Since the time when my first dynamo-electric machine 

 was invented, many important improvements have been 

 made, by myself and others, in the details of these machines 

 to render them more efficient for the several purposes to 

 which they have been applied. The first of such improve- 

 ments was the device of substituting the residual permanent 

 magnetism of iron for the magnetism of steel, as the initial 

 stage of the indefinite increase of the magnetism of the 

 electro-magnets. This happy device, which was hit upon 

 by several inventors almost simultaneously, consisted simply 

 in coupling up, by means of a short piece of wire, the 

 armature and electro-magnetic circuits of a dynamo-electric 

 machine, and involved no change either in the principle or 

 in the construction of my original machine. The residual 

 permanent magnetism of the large electro-magnet of this 

 machine, as I have already pointed out, was enormously 

 greater than that of the small steel magnets of the magneto- 

 electric machine which originally excited it. The principle, 

 therefore, of magnetic accumulation as first enunciated and 

 demonstrated by me is common to every class of dynamo- 

 electric machines. I should not have considered it necessary 

 to make these observations before members of the Society, 

 to whom the principles of these machines are well known, 

 were it not that writers of text-books who are unacquainted 

 with the extent of my researches, persist in setting up the 

 utilization of the residual magnetism of electro-magnets as 

 a principle in electrical science, than which nothing can be 

 more erroneous. 



" The utilization of the residual magnetism of electro- 

 magnets was soon followed by the improvements of 

 Pacinnoti and others in the construction and winding of the 

 armatures ; the object of which was the production of con- 

 tinuous currents, as distinguished from the alternating wave 



