148 Revolving Electric Magnet. 



Around the keeper, between the disks, are wound six hundred 

 and twenty feet of copper wire covered with silk in one magnet, and 

 four hundred and seventy five feet in the other. 



The ends of the wire are connected, the one with the keeper, and 

 the other with the inside of one of the poles of the magnet, and also 

 two other wires proceed, the one from the keeper and the other from 

 the outside of one pole of the magnet, in the manner of Mr. Emmet, 

 except that thumb screws, are added to make the metallic connection 

 raor6 perfect. These magnets give small, but brilliant sparks when 

 the keeper is slid horizontally off, especially when it is done with a 

 sudden and rapid motion ; in the dark, the spark was very vivid, and 

 exhibited the party colored hues of lightning. The best sparks were 

 obtained between the keeper and the poles of the magnet, and were 

 observed at the moment when the connection was broken. The 

 sparks from the points of the connecting wires were much more fee- 

 ble. .The shocks from these wires were felt distinctly in the finger 

 joints, and were very decided and even painful, when the wires were 

 connected with the tongue. Usually, the flash of light was not observ- 

 ed when the connection was made through the tongue only ; with the 

 stronger of these two magnets, however, this effect was observed ; and 

 when the wires of the weaker magnet were placed, one under the 

 tongue and the other between the upper lip and gum, the flash was dis- 

 tinct ; but it never failed with either, when one wire was laid on the 

 tongue and the other was made to touch the eye ball. As it was not 

 quite convenient to move a wire around the eye, a small disk of copper 

 (as large as a twelve and a half cent piece,) was soldered to the remote 

 end of one of the connecting wires ; when, to the moistened eye ball of 

 the closed eye, this disk was applied and the other wire touched to the 

 tongue, at the moment when the keeper was slid off, a flash was per- 

 ceived as brilliant as lightning, and the whole of that side of the face 

 received a convulsive twitch. All these effects, the spark, the shock 

 and the flashes of light, were perceived, without apparent diminution, 

 when the discharging wires were made to take a circuit of one hundred 

 and fifty feet, and the poles for discharge were made to meet in the 

 middle of this distance, that is, seventy five feet from the magnet — the 

 shocks through the fingers were very strong. It is a battei-y, always 

 charged, and whose energy is independent of chemical agency. — Ed. 



Electro- Galvanic Effects. 



It may perhaps be worth mentioning, that in using the great gal- 

 vanic magnet of Prof. Henry, which is excited by a small galvanic 



