Part I

-The Horizontal Bar [298]

Gymnastic apparatus costs money and needs to be housed, because it will not stand the weather. Gymnasiums are not always available for the average boy who likes exercise and who would like to learn the tricks on horizontal and parallel bars, horse and rings, which all young athletes are taught in regular gymnastic courses.

Any small crowd of boys--even two--having a few simple tools, a will to use them and the small amount of money required to buy the necessary

[Illustration: Adjustable Horizontal Bar

wood, bolts and rope, can make a first class gymnasium. If trees are convenient, and some one can swing an axe, the money outlay will be almost nothing. The following plans are for material purchased from a mill squared and cut to length. To substitute small, straight trees for the squared timbers requires but little changes in the plans.

The most important piece of apparatus in the gymnasium is the horizontal bar. Most gymnasiums have two: one adjustable bar for various exercises and a high bar for gymnastic work. The outdoor gymnasium combines the two. The material required is as follows: 2 pieces of wood, 4 in. square by 9-1/2 ft. long; 4 pieces, 2 by 4 in. by 2 ft. long; 4 pieces, 1 by 7 in. by 6-1/2 ft. long; 4 filler pieces, 3/4 by 3 in. by 3 ft. 9 in. long and 1 piece, 2-1/2 in. square by 5 ft. 7 in. long. This latter piece is for the bar and should be of well seasoned, straight-grained hickory. It makes no difference what kind of wood is used for the other pieces, but it is best to use cedar for the heavy pieces that are set in the ground as it will take years for this wood to rot. Ordinary yellow pine will do very well. The four 7-in. boards should be of some hard wood if possible such as oak, hickory, maple, chestnut or ash. The other material necessary consists of 2 bolts, 1/2 in. in diameter and 7 in. long; 16 screws, 3 in. long; 4 heavy screw eyes with two 1/2-in. shanks; 50 ft. of heavy galvanized wire: 80 ft. of 1/4-in. manila rope and 4 pulley blocks. Four cleats are also required but these can be made of wood at home.

Draw a line on the four 7-in. boards along the side of each from end to end, 1-1/4-in. from one edge. Beginning at one end of each board make pencil dots on this line 5 in. apart for a distance of 3 ft. 4 in. Bore holes through the boards on these marks with a 9/15-in. bit. Fasten two of these boards on each post with the 3-in. screws, as shown in the top view of the post Fig. 1, forming a channel of the edges in which the holes were bored. Two of the filler pieces are fastened in each channel as shown, so as to make the space fit the squared end of the bar snugly. The ends of the boards with the holes should be flush with the top of the post. This will make each pair of holes in the 7-in. boards coincide, so the 1/2-in. bolt can be put through them and the squared end of the bar.

Select a level place where the apparatus is to be placed and dig two holes 6 ft. apart, each 3 ft. deep and remove all loose dirt. The ends of the posts not covered with the boards are set in these holes on bricks or small stones. The channels formed by the boards must be set facing each other with the inner surfaces of the posts parallel and 5 ft. 8 in. apart. The holes around the posts are filled with earth and well tamped.

The hickory piece which is to form the bar should be planed, scraped and sandpapered until it is perfectly smooth and round except for 3 in. at each end. Bore a 9/16-in. hole through each square end 1-1/4 in. from the end. The bar may be fastened at any desired height by slipping the 1/2-in. bolts through the holes bored in both the bar and channel.

Each post must be well braced to keep it rigid while a person is swinging on the bar. Four anchors are placed in the ground at the corners of an imaginary rectangle 9 by 16 ft., in the center of which the posts stand as shown in Fig. 2. Each anchor is made of one 2-ft. piece of wood, around the center of which four strands of the heavy galvanized wire are twisted, then buried to a depth of 2 ft., the extending ends of the wires coming up to the surface at an angle.

The heavy screw eyes are turned into the posts at the top and lengths of ropes tied to each. These ropes or guys pass through the pulley blocks, which are fastened to the projecting ends of the anchor wire, and return to the posts where they are tied to cleats. Do not tighten the guy ropes without the bar in place, as to do so will strain the posts in the ground. Do not change the elevation of the bar without slacking up on the ropes. It takes but little pull on the guy ropes to make them taut, and once tightened the bar will be rigid.

[Illustration: Ground Plan]

Oil the bar when it is finished and remove it during the winter. It is well to oil the wood occasionally during the summer and reverse the bar at times to prevent its becoming curved. The wood parts should be well painted to protect them from the weather.

** Electrostatic Illumination [299]

Anyone having the use of a static machine can perform the following experiment which gives a striking result. A common tumbler is mounted on a revolving

[Illustration: Illuminated Tumbler]

platform and a narrow strip of tinfoil is fastened with shellac varnish to the surface of the glass as follows: Starting beneath the foot of the glass from a point immediately below the stem, it is taken to the edge of the foot; it follows the edge for about 1 in. and then passes in a curve across the base, and ascends the stem; then it passes around the bowl in a sinuous course to the rim, which it follows for about one-third of its circumference; after which it descends on the inside and terminates at the bottom. The tinfoil on the outside of the glass is divided by cutting with a knife every 1/8 in., the parts inside and beneath the glass being left undivided. Current is then led from a static machine to two terminals, one terminal being connected to one end of the tinfoil strip, and similarly the second terminal makes contact with the other end. As soon as the current is led into the apparatus, a spark is seen at each place where the knife has cut through the tinfoil. If the tumbler is rotated, the effect will be as shown in the illustration. A variety of small and peculiar effects can be obtained by making some of the gaps in the tinfoil larger than others, in which case larger sparks would be produced at these points. The experiment should be carried out in a darkened room, and under these circumstances when nothing is visible, not even the tumbler, the effect is very striking.

** Balloon Ascension Illusion [300] By C. W. Nieman

In these days of startling revelations in air-craft flight we are prepared to see any day some marvelous machine driven bird cutting figure-eights all over the sky above our heads. One boy recently took advantage of this state of expectancy to have an evening's harmless amusement, through an illusion which deceived even the most incredulous. He caused a whole hotel-full of people to gaze open mouthed at a sort of "Zeppelin XXIII," which skimmed along the distant horizon, just visible against the dark evening sky, disappearing only to reappear again, and working the whole crowd up to a frenzy of excitement. And all he used was a black thread, a big piece of cardboard and a pair of field glasses.

He stretched the thread between two buildings, about 100 ft. apart, in an endless belt, passing through a screweye at either end. On this thread he fastened a cardboard "cut-out" of a dirigible, not much to look at in daytime, but most deceptive at dusk. By pulling one or the other string he moved the "airship" in either direction. He took the precaution of stretching his thread just beyond a blackberry hedge and thus kept over-inquisitive persons at a safe distance. He also saw to it that there was a black background at either end so that the reversing of the direction of the craft would not be noticed.

In attracting the crowd he had a confederate stand looking at the moving ship through a field glass, which at once gave the suggestion of distance, and materially heightened the illusion. When the interest of the crowd, which at once gathered, was at its height, the "aeronaut" pulled his craft out of sight and let the disillusion come when the light of day laid bare his fraud.

** A Cork Extractor [300]

The device shown in the sketch is for removing a cork or stopper from a bottle whether full or empty where the cork has been pushed inside. A wire about No. 14 gauge is bent as shown at B, Fig. 1, to fit the index finger and the other end filed to a point C, and turned in a spiral D, so the point will be on top. Insert this tool in the bottle as shown in Fig. 2 and place the end D under the cork and pull up. The cork will come out easily. --Contributed by Maurice Baudier. New Orleans. La.

[Illustration: Cork Extractor]

** An Outdoor Gymnasium