[Illustration:  Plug]

A plug suitable for electric light extension or to be used in experimenting may be made from an old electric globe.  The glass is removed with all the old composition in the brass receptacle, leaving only the wires.  On the ends of the wires, attach two small binding posts.  Fill the brass with plaster of paris, and in doing this keep the wires separate and the binding-posts opposite each other.  Allow the plaster to project about 3/4 in. above the brass, to hold the binding-posts as shown.  —­Contributed by Albert E. Welch, New York.

** How to Make an Electric Fire Alarm [430]

On each end of a block of wood, 1 in. square and 1 in. long, fasten a strip of brass 1/4 by 3 in., bent in the shape as shown in the sketch at A, Fig; 1.  These strips should have sufficient bend to allow the points to press tightly together.  A piece of beeswax, W, is inserted between the points

[Illustration:  Fire Alarm Device]

of the brass strips to keep them apart and to form the insulation.  A binding post, B, is attached to each brass strip on the ends of the block of wood.  The device is fastened to the wall or ceiling, and wire connections made to the batteries and bells as shown in the diagram, Fig. 2.  When the room becomes a little overheated the wax will melt and cause the brass strips to spring together, which will form the circuit and make the bell ring.  Each room in the house may be connected with one of these devices, and all on one circuit with one bell.

** Home-Made Boy’s Car [430]

[Illustration:  Boys’ Home-Made Auto]

The accompanying cut shows how a boy may construct his own auto car.  The car consists of parts used from a boy’s wagon and some old bicycle parts.  The propelling device is made by using the hanger, with all its parts, from a bicycle.  A part of the bicycle frame is left attached to the hanger and is fastened to the main board of the car by blocks of wood as shown.  The chain of a bicycle is used to connect the crank hanger sprocket to a small sprocket fastened in the middle of the rear axle of the car.  The front axle is fastened to a square block of wood, which is pivoted to the main board.  Ropes are attached to the front axle and to the back part of the main board to be used with the feet in steering the car.  To propel the auto, turn the cranks by taking hold of the bicycle pedals. —­Contributed’ by Anders Neilsen, Oakland, Cal.

** Photographs in Relief Easily Made [431]

Relief photographs, although apparently difficult to produce, can be made by any amateur photographer.  The negative is made in the usual way and,

[Illustration:  Reproduced from a Relief Photograph]