The diagonal struts, B, should be cut a little too long, so that they will be slightly bowed when put in position, thus holding the cloth out taut and flat.  They should be tied together at the points of intersection and the ends should be wound with coarse harness maker’s thread, as shown at C, to prevent splitting.  The small guards, D, are nailed or glued to the longitudinal sticks to prevent the struts slipping out of position.  Of course the ends of the struts could be fastened to the longitudinal strips if desired, but if made as described the kite may be readily taken apart and rolled up for convenience in carrying.

The bridle knots, E, are shown in detail at H and J. H is a square knot, which may be easily loosened and

[Illustration:  Detail of Box Kite]

shifted to a different position on the bridle, thus adjusting the lengths of F and G. A bowline knot should be tied at J, as shown, to prevent slipping.  If the kite is used in a light wind, loosen the square knot and shift nearer to G, thus shortening G and lengthening F, and if a strong wind is blowing, shift toward F, thereby lengthening G and making F shorter.  In a very strong wind do not use the bridle, but fasten a string securely to the stick at K.  —­Contributed by Edw.  E. Harbert, Chicago.

** Lubricating a Camera Shutter [58]

An experienced photographer uses blacklead [graphite] for grooves about a camera or holder.  A small quantity is rubbed well into the grooves and on the edges of shutters, that refuse to slide easily, with gratifying results.  Care must be taken to allow no dust to settle in the holders, however.

** Simple Open-Circuit Telegraph Line [59]

By using the circuit shown in the sketch for short-distance telegraph lines, the extra switches and wiring found in many circuits are done away with.  Closing either key will operate both sounders, and, as the resistance of

[Illustration:  Simple Telegraph Line]

the sounders is very high, the batteries do not run down for a long time.  —­Contributed by A. D. Stoddard, Clay Center, Kan.

** How to Make a Thermo Battery [59]

A thermo battery, for producing electricity direct from heat, can be made of a wooden frame, A, with a number of nails, B, driven in the vertical piece and connected in series with heavy copper wires, C. The connections should all be soldered to give good results, as the voltage is

[Illustration:  Thermo Battery]

very low and the resistance of an unsoldered joint would stop the current.  The heat may be supplied by an alcohol lamp or other device, and the current may then be detected by means, of a simple galvanometer consisting of a square spool of No. 14 or No. 16 single-covered wire, E, with a pocket compass, F, placed on top.  Turn the spool in a north and south direction, or parallel with the compass needle.  Then, when the nail heads are heated and the circuit completed, the needle will swing around it at right angles to the coils of wire.  Applying ice or cold water to the nail heads will reverse the current.  —­Contributed by A. C. A., Chicago.