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 bands should be made to the exact dimensions given in the sketch and fastened to the four longitudinal sticks with 1 oz. tacks.  It is well to mark the positions of the sticks on the cloth bands, either with a soft lead-pencil or crayon, in order to have the four sides of each band exactly equal.  The ends of the bands should be lapped over at least 1/2 in. and sewed double to give extra strength, and the edges should be carefully hemmed, making the width, when finished, exactly 12 in.  Probably the best cloth for this purpose is nainsook, although lonsdale cambric or lightweight percaline will answer nearly as well.