Finally arrange them so that they are on the bottom, facing each other bow to bow, two or three inches apart (1, Fig. 35), and release the stopper quickly. Do the submarines try to ram each other (2, Fig. 35) in a most realistic manner? [Illustration: FIG. 37 AN AIR GUN ] Experiment 23. To flare the end of a tube. Heat the end of a piece of No. 2 tube until it is red hot, take it out of the flame, hold the flaring wire inside the end, and press outward gently while you revolve the tube (1, Fig. 36). Do you find that the end is flared out (2, Fig. 36)? Experiment 24. To make an air gun. Take a full length piece of No. 4 tube and flare both ends slightly. This is the air gun (Fig. 37). Now to make an arrow, cut off the lighting end of a match and insert a pin in the other end (Fig. 38). [Illustration: FIG. 38 THE ARROW IS SHOT PIN-END FIRST ] Insert this arrow in the air gun and blow it out. Does it come out with considerable speed? Experiment 25. A shooting match. [Illustration: FIG. 39 A SHOOTING MATCH ] Draw a target on a piece of paper and hang it up, away from the wall or at the edge of the table, where there will be space behind for the arrows to pass through. Now shoot at the target with your air gun (Fig. 39). Do you find that the arrow makes holes in the target and sometimes goes right through? The bull’s-eye of a target is usually 1 inch in diameter, the next circle outside is 2 inches in diameter, the next 4 inches, and the outer circle 5 inches. Get up a shooting match and keep track of the score made by each. If the bull’s-eye is cut anywhere by the arrow, the count is 5 points; a cut anywhere inside or touching the 2-inch circle counts 4 points; anywhere inside or touching the next two circles counts 3 and 2 points respectively. The one who makes the highest score in five shots is the winner. It is more sanitary if each shooter has his own air gun and arrows. Experiment 26. Height and distance contest. Go outside and see which of you can shoot his arrow to the greatest height and to the greatest distance. Give each contestant five shots. [Illustration: FIG. 40 THE PEA SHOOTER IN ACTION ] You can make fair estimates of the heights if you shoot up beside a building or tall tree. Experiment 27. To make a pea shooter. [Illustration: FIG. 41 BENDS ] Take a full length piece of No. 6 tubing, smooth both ends and flare them out slightly. This makes an excellent pea shooter. Try it with peas. Do you find that they come out with great speed? Experiment 28. A pea-shooting match. Make a target on a piece of paper, hang it up away from the wall or at the edge of the table, and shoot at it (Fig. 40). Do you find that the peas go right through the paper? Arrange a match with your friends and keep track of the score as in Experiment 25. Experiment 29. To make a good bend.