III. ELECTRO-MAGNETS. 281 



III. ELECTRO-MAGNETS AND ELECTRO-MAGNETIC 

 ENGINES. 



1115. Large Electro-Magnet, for showing magnetism and 

 diamagnetism. Elliott Brothers. 



1115a. Small Electro-Magnet by M. cFObelliane, bearing 

 thirty times its own weight. Polytechnic School, Paris. 



1116. Three Electro-Magnets. 



The Committee, Royal Museum, Peel Park. Salford. 



One of which is a circular plate, 4^ inches diameter ; another, a plate 

 4^ inches square ; and the third, 4 inches, with one armature ; the 4-inch 

 magnet will sustain a load of 1,400 Ibs. to 1,500 Ibs. Made by the late 

 R. Roberts, C.E., of Manchester. 



1117. Powerful Electro-Magnet. 



The Committee, Royal Museum, Peel Park, Salford. 



Of the horse-shoe form, with an elliptical section. Made by the late 

 R. Roberts, C.E., of Manchester. 



1118. Surface Electro-Magnet made in 1840. When fully 

 excited, the armature is retained with a force of upwards of a ton. 



J. P. Joule, D.C.L., F.R.S. 



1119. Electro-Magnet, on Joule's Construction, mounted 

 so as to serve for supporting weights, or for experiments on Dia- 

 magiietism. Dr. Stone. 



1119a. Electro-Magnet, by Repmann. 



M. Breguet, Paris. 



1119b. Electro-Magnet, by Jablochkoff. 



M. Breguet, Paris. 



1119a. Small Electro-magnet. H. L. Rutter. 



10 2O. Tubular Electro-Magnets. John Faulkner. 



In this system iron cases are used, of such size and thickness as ensures 

 the utilisation of the maximum magnetic effect. 



The object is to accumulate and utilise all or a portion of the electric power, 

 and thereby when desirable prevent the loss that takes place in electro- 

 magnets usually employed in electrical appliances. 



1121. Diagrams (30), illustrating the Great Waste of 

 Power in Electro-Magnets as heretofore made, and the 

 economy of tubular electro-magnets. John Faulkner. 



These diagrams are produced by. scattering iron filings upon paper, prepared 

 with paraffin, placed above ordinary electro- magnets and improved electro- 

 magnets respectively. 



