** A Concrete Swimming Pool [178]

[Illustration:  Home-Made Swimming Pool]

Several boys from a neighborhood in the suburbs of a large city concluded to make for themselves a swimming tank of concrete.  The money was raised by various means to purchase the cement, and the work was done by themselves.  The ground was selected in a secluded spot in a neighbor’s back yard and a hole dug to a depth of 4 ft., 12 ft. wide and 22 ft. long.  The concrete was made by mixing 1 part cement, 4 parts sand and 10 parts gravel together and the bulk moistened with water.  The bottom was made the same as laying a sidewalk, and forms were only used for the inside of the surrounding wall.  The tank may be hidden with shrubbery or vines planted to grow over a poultry wire fence.

** Old-Time Magic-Part IV [179]

Cutting a Thread Inside of a Glass Bottle [179]

This is a trick which can only be performed when the sun shines, but it

[Illustration:  The Glass Directs the Sun’s Rays]

is a good one.  Procure a clear glass bottle and stick a pin in the lower end of the cork.  Attach a thread to the pin and tie a small weight to the end of the thread so it will hang inside the bottle when the cork is in place.  Inform your audience that you will sever the thread and cause the weight to drop without removing the cork.

All that is required to perform the feat is to hold a magnifying glass so as to direct the sun’s rays on the thread.  The thread will quickly burn and the weight fall.

** Removing a Key from a Double String [179]

Tie the ends of a 5-ft. string together, making a double line on which a key is placed and the string held as shown by the dotted lines in the sketch.  Turn the palms of the hands toward you and reach over with the little finger of the right hand and take hold of the inside line near the left-hand thumb.

[Illustration:  “The Key Will Drop from the String”]

Reverse the operation and take hold of the inside line near right-hand thumb with the little finger of the left hand.  You will then have the string as it appears in the sketch.  Quickly let loose of the string with a little finger on one hand and a thumb on the other and pull the string taut.  The key will drop from the string.

** How to Bore a Square Hole [179]

You would not consider it possible to bore a square hole in a piece of cardboard, yet such a thing can be done.  Take a cardboard or a thin piece of wood, fold and place it between two pieces of board with the fold up; the boards are then put in a vise as shown.  Start the bit with the screw point in the fold, using a 1-in. bit, and bore a

[Illustration:  Boring a Square Hole]

hole 1/2 in. deep.  When the cardboard is taken from the vise it will appear as shown at B and when unfolded, as at A.

** How to make copper trays [180]