448 Messrs. Scoresby and Joule on the Mechanical 



forces, these again depending on the quantities of electricity 

 and matter in the atoms. This has been merely hinted at, not 

 for explanation, but to show that the theory gives the property 

 referred to, to inherent powers in bodies themselves, and not 

 to the space in which they are situated, and by which they are 

 surrounded. My reasons for considering the atoms of bodies 

 as mere centres of force, have not been given, as they are con- 

 nected with other subjects on which you may not be able to 

 afford space for entering. 



I am, Sir, 

 Killigrew St., Falmouth, Yours, &c, 



Jan. 19, 1846. Henry Sloggett. 



LXXV. Experiments and Observations on the Mechanical 

 Powers of Electro- Magnetism, Steam, and Horses. By the 

 Rev. William Scoresby, D.D., F.R.SS. L. and E., Corr. 

 Memb. Inst. Fr., tyc, and James P. Joule, Secretary of the 

 Literary and Philosophical Society of Manchester, Mem. 

 Chem. Soc, fyc* 



A T the last Meeting of the British Association, Dr. Scoresby 

 ■**■ described a magnetic apparatus of very great power, and 

 gave an account of some experiments he had made with a view 

 to test its capabilities for exciting electrical currents. The 

 coils employed in those experiments were hastily constructed, 

 and by no means calculated to produce a maximum effect. 

 We agreed, therefore, to construct and try more efficient ones 

 on the first opportunity. 



Two kinds of revolving armature occurred to us as worthy 

 of trial. One of them consisted of a hollow tube of drawn 

 iron, 24 inches long, l^th inch in diameter, and T 3 gths of an 

 inch thick in the metal, bent into the shape of the letter U. 

 It had a saw-cut along its entire length, in order to prevent 

 the circulation of electrical currents in the substance of the 

 iron. Each of the legs of this armature was wound with 274 

 feet of covered copper wire, y^th of an inch in diameter. The 

 other armature consisted of two bars of iron, each 20 inches 

 long, 4 inches broad, and fths of an inch thick. These bars 

 were bent edgeways into the form of a semicircle, and then 

 fastened together with the interposition of a piece of calico in 

 order to prevent currents in the iron as much as possible. 

 Each leg of this armature was furnished with two coils of co- 

 vered copper wire y^th of an inch thick. The two coils that 

 were nearest the iron were each 276 feet long; and each of 

 the other two coils was 296 feet long. 



* Communicated by the Authors. 



