MAGNETO-ELECTRIC MACHINES. 



Fig. 469. 



There is a steel rasp at the side of the instrument, which is 

 used when the greatest effect is wanted, in which case the 

 wire from the battery that is nearest the electro-magnet is 

 taken out of the cup and grated along the rasp, which will 

 increase the power much, though the armature will stop re- 

 volving. The intensity of the power may be much increased 

 by wetting the part to which it is applied with water or 

 vinegar, and also varied by grasping or pressing the handles 

 or conductors. The silver spring requires to be adjasted 

 with care, and should gently touch the break-piece where it 

 is filed away, touching twice in each revolution. If it press 

 the break-piece too hard it 

 will stop the armature ; if it 

 does not touch, the current 

 cannot, flow. Also keep the 

 zinc cylinder from any con- 

 tact with the copper. The 

 machine is packed in a neat 

 case, sixteen inches long, 

 six inches wide, and seven 

 inches deep, and has a pair 

 of handles, a pair of insulat- 

 ed coppers, and a foot-plate 

 with the necessary wires, 

 and a number of papers of 

 blue vitriol for the battery ; 

 the form of battery will 

 keep this instrument five 

 times as long in action as 

 the square batteries in use, 

 having the same quantity 

 of blue vitriol. 



Price, $14.00. 



Vibrating Magnetic In- 

 strument for Medical use, 

 (Fig. 469.) In this ar- 

 rangement the armature, 

 instead of revolving, vi- 

 brates between the platina 

 point and one of the poles 

 of the magnet, the armature 

 being in the form of a small 



