e little can, is perforated with a
number of holes. This can C is filled about half full of broken
pieces of carbide and then placed in the little can D. A gas cock,
H, is soldered onto tank A, as shown, from which the gas may be
taken through a rubber tube. Fill tank B with water and set tank A
into it. This will cause some air to be enclosed, which can be
released by leaving the cock open until tank A settles down to the
point where the water will begin to run in the perforations of the
little tank. The water then comes in contact with the carbide and
forms gas, which expands and stops the lowering of tank A. Then
the cock must be closed and tubing attached. It is dangerous to
attempt to strike a match to light a jet or the end of the cock
while air is escaping and just as the first gas is being made.
Wait until the tank is well raised up before doing this.
--Contributed by James E. Noble, Toronto, Ont.

** Homemade Annunciator [57]

When one electric bell is operated from two push-buttons it is
impossible to tell which of the two push-buttons is being operated
unless an annunciator or similar device is used. A very simple
annunciator for indicating two numbers can be made from a small
box, Fig. 1, with an electric-bell magnet, A, fastened in the
bottom. The armature, B, is pivoted in the center by means of a
small piece of wire and has an indicator or hand, C, which moves
to either right or left, depending on which half of the magnet is
magnetized. If the back armature, D, of the magnet is removed the
moving armature will work better, as this will prevent the
magnetism from acting on both ends of the armature.

The wiring diagram, Fig. 2, shows how the connections are to be
made. If the pushbutton A is closed; the bell will ring and the
pointer will point at 1,

[Illustration: Annuciator and Wiring Diagram]

while the closing of the push-button B will ring the bell and move
the pointer to 2.
--Contributed by H. S. Bott, Beverly, N. J.

** How to Make a Box Kite [58]

As some of the readers of Amateur Mechanics may desire to build a
box kite, a simple method of constructing one of the modern type
is given in detail as follows: The sticks should be made of
straight grained wood, which may be either spruce, basswood or
white pine. The longitudinal corner spines, A A, should be 3/8 in.
square by 42 in. long, and the four diagonal struts, B, should be
1/4 in. by 1/2 in., and about 26 in. long. Two cloth