get out at any
other place than at Y. As soon as the bolts were magnetized, L was
forcibly drawn down, pulling F away from I, thus opening the circuit.
As the bolts were no longer magnets, F sprang right back to I, the
current passed long enough to re-magnetize the bolts. This operation was
rapidly repeated.

218. Use. If you wish to use the buzzer simply to call some one
occasionally, a dry battery or Leclanche cell is best. This apparatus is
good to work a gravity cell when it needs regulating.

APPARATUS 126.

[Illustration: Fig. 101.]

_219. Electric Bell._ Fig. 101. Before making this bell, carefully read
the directions and explanations given for the electric buzzer, App. 125.
The parts are very much alike in the two instruments, and most of the
lettering of them has been made the same in the illustrations. If you
look at Fig. 101 from the side, with the letters M and Q at the bottom,
you will see that this bell is merely a modified form of App. 125.

The Base is 7 x 5 x 1/2 in. To the upper end of this is nailed the
cross piece, D. To D are fastened the binding-posts.

The Parts, F, G, H, I, J, K, L, M, N, P, Q, are the same as explained in
App. 121 and 125.

The Magnet is fastened to the base by a tin strip, C, which is screwed
down at both ends. By nailing a strip, like D, along the left side of
the base, the magnet may be fastened to this. This strip would take the
place of the base of App. 125.

The piece, F, of two thicknesses of tin, is made longer than it was in
App. 125; in fact, it projects through L and forms the part N. To the
lower end of N is fastened a large bullet. Hold the cutting-edge of a
strong knife-blade upon the bullet, and with a few taps of a hammer
drive the blade into it to make a gash.

Put the end of N into the cut, then hammer the bullet so that N will be
pinched. If you have no bullet, cut a long strip of tin, about 3/8 in.
wide, and wind this about the end of N to serve as a ball.

The Bell, E, may be taken from an old alarm-clock. This is not screwed
directly to the base, as it would not ring well. After you have the
ball, O, properly fixed, hold E, so that O will strike it near its rim;
then cut a piece of wood about 5/8 x 5/8, and long enough to put under
E, to raise its rim to the right place. This piece must be screwed to
the base from the underside, and on to its top is placed the screw which
passes through the bell. In other words, E is mounted upon a rod which