Revolving Electric Magnet. 147 



of mercury, and the other brought close to the surface of the mer- 

 cury, d, d', wheels and a band to cause the magnet to rotate on its 

 axis e. F, F', table to support the machinery. 



" The magnet should be armed with its connecting bar, which 

 should come close to the extremities of the multiplicator without 

 touching it. When the magnet is made to revolve and the extremity 

 of the poles are approximated as above directed ; there is a con- 

 stant current of electricity, which becomes visible to the eye, a spark 

 like a twinkling star being given off jrom the pole brought near the 

 surface of the mercury. The spark is accompanied by an audible 

 crackling sound, and is easily seen even by day light. 1 tried to 

 take a shock from the wires but the intensity of the spark was not 

 sufficiently great to produce any commotion. When one of the 

 wires is placed on and the other under the tongue, there is a strong 

 .metallic taste, like that produced by pieces of silver and zinc placed 

 in a similar manner when brought in contact. 



" It would appear, then, that the quantity of electricity is great, 

 but its intensity feeble. If we were able to produce a sufficiently 

 strong magnet, there can be no doubt that this steady current of 

 electricity, given off without any expense of acid or any diminution 

 of intensity, might be of practical utility in the arts." 



Experiments in the Laboratory of Yale College. — Sparks and 

 Shocks from the Magnet. 



Two magnets have been made, under my direction, by Messrs. Brad- 

 ley SiMerriman, of this place, (New Haven,) upon the plan of Prof. 

 Emmet, as described in the present number of this Journal, p. 78. 



These magnets consist, each, of nine plates, seven eighths of an 

 inch wide, a little more than one eighth of an inch thick, and thirteen 

 inches long, all united by a screw which perforates them. They are 

 in the usual horse shoe form, and the space between the poles is three 

 inches. They are capable of supporting over twenty pounds each. 



The armature or keeper, which is in the form of a flat bar, is six 

 inches long, seven eighths of an inch wide, and three eighths of an 

 inch thick. It perforates two wheels or disks of plate brass, each of 

 three inches and a half diameter, and covered with silk on the inside 

 and with shell lac varnish on the outside. 



These disks, when the armature, or keeper is in them, exactly 

 resemble wheels on an axletree ; they are placed at the distance of 

 three sixteenths of an inch from the poles of the magnet, when the 

 keeper rests in such a position as to divide the distance equally. 



