102 Mr. H. Wilde's Experimental Researches 



placed in the magnet-cylinder, for the purpose of avoiding the 

 excessive vibrations which were produced when they revolved at 

 high velocities without being balanced. By means of a small 

 carriage, the quantity and intensity armatures could easily be 

 withdrawn from the magnet- cylinder, and interchanged, when 

 required, in the course of a few minutes, the cross-head at the 

 driving end of the machine being readily immoveable for that 

 purpose. 



74. Though the total weight of the 10-inch, electromagnetic 

 machine complete is very considerable, being nearly 4*5 tons, 

 yet its dimensions are comparatively small, since the entire length 

 of the machine, including the brass cross-heads, is only 80 inches, 

 its width 24 inches, and its height 60 inches. 



75. Experiments were first made with the machine, for the 

 purpose of testing its power when the large electromagnet was 

 excited by magneto-electric and electromagnetic machines of 

 various sizes. The 10-inch machine, as well as the machines 

 used for exciting it, were all driven from the same countershaft 

 by means of pulleys of suitable dimensions. The intensity and 

 quantity armatures (71, 72) were driven at a uniform velocity 

 of about 1500 revolutions per minute, by means of a broad 

 leather belt of the strongest description. The springs for taking 

 the electricity from the 10-inch machine were connected, by 

 means of large copper conductors, with two insulated plates of 

 copper let into the underside of an experimental table. On the 

 upper side of this table were two moveable brass studs, sliding 

 in good contact with the copper plates, and forming the polar 

 terminals of the machine. 



76. The quantity armature was first placed in the cylinder, 

 and the springs were so arranged as to take the alternating cur- 

 rents of electricity from the polar terminals (16). The direct 

 current from the small magneto-electric machine, having on its 

 cylinder six permanent magnets, such as were used in the first 

 series of experiments (12), was then transmitted through the 

 coils of the electromagnet of the 5 -inch electromagnetic ma- 

 chine (63) ; and the direct current from the latter was simulta- 

 neously, and in like manner, transmitted through the coils of 

 the electromagnet of the 10-inch machine. 



77. This combination of the machines, when in full action, 

 was attended by the development of an amount of magnetic 

 force in the large electromagnet far exceeding anything which 

 had hitherto been produced, together with the evolution of a 

 quantity of dynamic electricity from the armature so enormous 

 as to melt pieces of cylindrical iron rod 15 inches in length, and 

 fully one- quarter of an inch in diameter. With the same ar- 

 rangement, the electricity from the quantity armature also 



