If you cannot readily procure a U-tube, you can make one, as I did, and the work is interesting.

The U-tube is constructed in the following manner.  A glass tube is closed at one end.  This is done by holding the tube in one corner of a gas flame, somewhat near the dark area (A, Fig. 2), and constantly turning the tube, when it will be found that the glass has melted together.  Now, after it is cool, about 3 or 4 in. from the sealed end, the tube is held steadily so that the flame will heat one small portion ( B, Fig. 2 ).  After this small portion is heated blow into the tube, not very hard, but just enough to cause tube to bulge out.  Allow to cool.  Then reheat the small bulged portion, blow quite hard, so that the glass will be blown out at this point, forming a small hole.  Now insert about 1/2 in. of platinum wire and reheat, holding platinum

[Illustration:  Making the U-Tube]

wire by means of a small pliers so that it will be partly in the tube and partly without.  The platinum will stick to the glass, and if glass is sufficiently heated one will be able to pull it, by means of pliers, from one side of the hole to the other, thus sealing the wire into the tube.  Another wire is sealed in the same way about 1 in. from the first.  Now, to bend the tube, one must hold it, with both hands, in the flame and turn constantly until soft.  Quickly withdraw from flame and bend, just as you would a piece of copper wire.  Allow to cool slowly.

The several tubes are connected with a short piece of rubber tubing.

The total cost of materials for constructing the apparatus complete will not amount to more than one dollar.  —­Contributed by M. G. Kopf, Lewis Institute, Chicago.

** Weatherproofing for Tents [389]

Dissolve 4 oz. sulphate of zinc in 10 gal. water; add 1/2 lb. sal-soda; stir well until dissolved, and add 1/2 oz. tartaric acid.  Put the tent cover in this solution and let lie 24 hrs.  Take out (do not wring it) and hang up to dry.  Grinnell’s Hand Book on Painting.

** Sawing Sheet Metal [389]

Sheet metal placed between two boards in the jaws of a vise and clamped tightly, can be sawed easily with a hacksaw.

** A Monoplane Weather Vane [390]

The toy windmill or weather vane shown in the sketch is made to represent a Bleriot monoplane.

[Illustration:  Wire and Sheet-Metal Vane]

The propeller is turned by the wind.  The frame is made of heavy wire and connected with straps of tin.  The construction is plainly shown in the illustration.  The windmill vane can be made in any size to suit the builder.  —­Contributed by W. C. Bliss, St. Louis, Missouri.

** How to Make a Minnow Trap [390]

Glass minnow traps that will give as good service as those purchased at the tackle store can be made without difficulty.  If a trap should be banged carelessly against the side of the boat or some other obstruction and smashed, instead of spending several dollars to replace it, a half hour’s time will turn out a new one just as good, says a correspondent of Outing.