372 Researches in Magnetic Electricity. 



terminations of the small wire, d, I, the terminations of the large 

 wires. 1, is a wooden strap, which, with a binding-screw, secures 

 the magnet to the wooden block k. s is a brass strap, to hold 

 firmly the poles of the magnet, e is the armature of soft iron^ 

 which, with the small brass pulley, is fitted firmly to the shaft, 

 o, the multiplying wheel, n, is the break -piece, which is merely 

 a copper ferule dissected, and filled up with wood or ivory, as 

 represented by the black spaces. /, one of the magnet wires bent 

 up, plays upon the whole portion of the ferule ; and m, one of the 

 battery wires, plays upon the break-piece. The other ba.ttery 

 wire is to be connected with the mercury cup d. Adjust now the 

 break-piece, 7i, or the copper wire, m, so that the circuit shall be 

 broken at the time or immediately after the armature leaves the 

 magnet, and turn the multiplying wheel o. The sparks and 

 shocks thus produced, will be found far greater than when the 

 circuit is broken while the armature is approaching. The break- 

 piece is readily adjusted, so that the armature revolves of itself 

 with great rapidity ; but in this case also, the sparks and shocks* 

 are at once diminished, as the source of magnetism must be cut 

 off before the armature arrives at its equilibrium. With things 

 thus arranged, connect the two ends of the small wire b, c. (This 

 wire is insulated, and entirely independent of the large wire.) 

 The revolution of the armature is now suddenly stopped. The 

 flowing of the secondary current after the galvanic is broken, 

 keeps up or prolongs the power of the magnet so as to retain the 

 armature. As a proof of this, set the spring and break-piece so 

 that the magnetic power shall be cut off, some time before the 

 armature arrives at equilibrium. It revolves of course slowly. 

 Connect now the ends of the small wire 6, c, and it immediately 

 revolves with rapidity, the prolongation of magnetism by the 

 secondary, contributing now to the motion of the bar. Here then 

 the secondary becomes a new source of magnetic power. This 

 instrument, when the armature is revolved mechanically, affords 

 a shock from Z>, c, both when the circuit is completed and broken. 

 The sparks are exceedingly brilliant, and the shocks so powerful 

 that they are sometimes felt by the bystanders through the floor. 

 The light from charcoal points is intense. It decomposes pure 

 water, and charges the Leyden jar. But its most remarkable and 

 novel property is that of giving a slight shock without breaking 



* The shocks are taken from the cups h^ c. 



