[Illustration:  Gasoline Burner]

of only 1 in.  One end of the copper tube is bent around so it will point directly into the reamed-out hole in the end of the brass tube, A. A nipple, N, is made by drilling a 1/8-in. hole halfway through a piece of brass and tapping to screw on the end of the 1/8-in. copper pipe.  A 1/64-in. hole is then drilled through the remaining part of the nipple.  The other end of the copper tube is connected to the supply tank.  The distance between the nipple, N, and the ends of the tube, A, should be only 5/16 of an inch.  Fig. 2 shows the end view.

** A Homemade Telephone Receiver [55]

A telephone receiver that will do good work may be built very cheaply as follows:  For the case use an ordinary 1/2-lb. baking-powder box with a piece of heavy wire soldered on the inside, 1-5/16 in. from the bottom.  For the magnet use a piece of round hardened steel about 3/8 in. in diameter and 1-1/4 in. long.  If desired, a piece of an old round file may be used for the magnet core, which should be magnetized previous to assembling, either by passing a current of electricity around it, or by direct contact with another magnet.  The steel core should be wound with about 250 ft. of No. 36 insulated wire, the ends of which should be soldered to a piece of

[Illustration:  Telephone Receiver]

lamp cord, passed through a hole in the bottom of the can and knotted inside to prevent pulling out.

A disk of thin sheet-iron, such as is used by photographers for tintypes (Ferrotype), should be cut to the diameter of the can, taking care not to bend the iron.  The magnet should then be placed in the bottom of the can in an upright position and enough of a melted mixture of beeswax and resin poured in to hold it in position.

While the wax is still in a plastic condition the magnet should be located centrally and adjusted so that the end will be 1/16 in. or less below the level of the top of the copper ring.

After the wax has hardened the disk is slipped in and fastened tightly by a ring of solder when the instrument is ready for use.

** How to Bind Magazines [56]

An easy way to bind Popular Mechanics in volumes of six months each is to arrange the magazines in order and tie them securely both ways with a strong cord.  It is well to put two or three sheets of tough white paper, cut to the size of the pages, at the front and back for fly leaves.

Clamp the whole in a vise or clamp with two strips of wood even with the back edges of the magazines.  With a sharp saw cut a slit in the magazines and wood strips about 1/2 in. deep and slanting as shown at A and B, Fig. 1.  Take two strips of stout cloth, about 8 or 10 in. long and as wide as the distance between the bottoms of the sawed slits.  Lay these over the back edge of the pack and tie securely through the slits with a string thread—­wrapping and tying several times (C, Fig. 2).