190 



XXVII. On ElectrO'7nag7ietic Motive Machines. By Mr, 

 Francis Watkins. 



[With a Plate.] 



To the Editors of the Philosophical Magazi?ie and Journal, 



Gentlemen, 

 pERMIT me in the pages of your next number to describe 

 -*- two or three modifications I have made in electro-magnetic 

 motive machines, for 1 am incHned to think that any new ar- 

 rangement of the working parts will interest those of your 

 readers who hope to see realised the expectations which have 

 been so confidently held out of successfully employing electro- 

 magnetic power for propelling machinery. 



We are indebted to Professor Joseph Henry, New Jersey 

 College, Princeton, for the first hint, and for the first con- 

 trivance wherein electro-magnetic power is made to produce 

 continuous motion. 



In one of Silliman's American Journals for 1831 will be 

 found Professor Henry's original description of his electro- 

 magnetic motive machine, and as I believe it is not very ge- 

 nerally known, I venture upon a brief description of it in this 

 place. It consists of an electro-magnetic beam, supported 

 horizontally on an axis passing through its centre of gravity, 

 with two permanent steel bar magnets arranged vertically, one 

 under each pole, of the horizontal electro-magnet, with their 

 north poles uppermost. Without entering into the details 

 of the method of changing the polarity of the mobile hori- 

 zontal electro-magnet, the working of the machine will, I 

 conceive, be sufficiently understood when it is stated, that by 

 a timely alteration of the magnetic polarity (which is effected 

 by changing the direction of the electric current inducing the 

 polarity) of the horizontal electro-magnetic beam, an alternate 

 series of attractions takes place between its poles and the poles 

 of the vertical permanent steel magnets, and thus a recipro- 

 cating rectilinear motion is obtained by the vibration of the 

 horizontal electro-magnetic beam. 



Since Professor Henry's publication several modified forms 

 of apparatus have been produced for exhibiting the electro- 

 magnetic power. In England, as far as my knowledge ex- 

 tends, little as yet has been achieved beyond the construction 

 of some very ingenious trifling machines or toys for exhibiting 

 continued rotatory motion by this agent. 



Several philosophers on the Continent have published ac- 

 counts of experiments, and of machines made by them, their 



