Two other types of boomerangs are illustrated herewith and they can be made as described.  The materials necessary for the T-shaped boomerang are:  One piece of hard maple 5/16 in. thick, 2-1/2 in. wide, and 3 ft. long; five 1/2-in. flat-headed screws.  Cut the piece of hard maple into two pieces, one 11-1/2 in. and the other 18 in. long.  The corners are cut from these pieces as shown in Fig. 2, taking care to cut exactly the same amount from each corner.  Bevel both sides of the pieces, making the edges very thin so they will cut the air better.  Find the exact center of the long piece and make a line 1-1/4 in. on each side of the center and fasten the short length between the lines with the screws as shown in Fig. 3.  The short piece should be fastened perfectly square and at right angles to the long one.

The materials necessary for the cross-shaped boomerang are one piece hard maple 5/16 in. thick, 2 in. wide and 30 in. long and five 1/2-in. flat headed screws.  Cut the maple- into two 14-in. pieces and plane the edges of these pieces so the ends will be 1-1/2 in. wide, as shown in Fig. 4.  Bevel these pieces the same as the ones for the T-shaped boomerang.  The two pieces are fastened together as shown in Fig. 5.  All of the boomerangs when completed should be given several coats of linseed oil and thoroughly dried.  This will keep the wood from absorbing water and becoming heavy.  The last two boomerangs are thrown in a similar way to the first one, except that one of the pieces is grasped in the hand and the throw given with a quick underhand motion.  A little practice is all that is necessary for one to become skillful in throwing them.  —­Contributed by O. E. Tronnes, Wilmette, Ill.

** How to Make Water Wings [202]

Purchase a piece of unbleached muslin, 1 yd. square.  Take this and fold it over once, forming a double piece 1-1/2 ft. wide and 3 ft. long.  Make a double stitch all around the edge, leaving a small opening at one corner.  Insert a piece of tape at this corner to be used for tying around the opening when the bag is blown up.  The bag is then turned inside out, soaked with water and blown up.  An occasional wetting all over will prevent it from leaking.  As these wings are very large they will prevent the swimmer from sinking.  —­Contributed by W. C. Bliss, St. Louis, Mo.

** How to Make an Ammeter [203]

The outside case of this instrument is made of wood taken from old cigar boxes with the exception of the back.  If carefully and neatly made, the finished instrument will be very satisfactory.  The measurements here given need not be strictly followed out, but can be governed by circumstances.  The case should first be made and varnished and while this is drying, the mechanical parts can be put together.

[Illustration:  Details of an Ammeter]