ANY boy can make a submarine boat of small size which will go down to the bottom of the lake or river and then come up again of itself, as shown in Figure I.

The body of this toy is sawed out of inch wood into the shape of a submarine about two feet long.

In outline it is sausage shape with a little special hump on top shaped like a boat, which is meant to stick out of the water when the toy is floating. On top of this a round stick gives the appearance of a periscope.

At the rear are some rudders made of tin, while in the center is a sort of triangular box pivoted on some bearings at the bottom and held upright in place by a little trigger.

The stones in the box form a weight, and enough are put in so that they will just sink the boat when it is set in the water. After the stones are in, set the trigger to hold the box from upsetting. When the submarine is fixed this way and put in the water, it sinks, and as it sinks, the rudders steer it forward. The minute it gets to the bottom, or near the bottom, the lower arm of this trigger or lever, T, in Figure 1, strikes bottom, and thus pulls itself out of the notch in the top of the weight box P. When this trigger is released, the box is pivoted on its lower corner, and immediately the weight in the box upsets it and dumps all the stones out, as shown in Figure 2.

Completed Submarine about to Strike Bottom.

Now, when these stones are out, the submarine is light enough to float, and it comes to the surface, the weight of the tin box and trigger below keeping it right side up. Figures 2, 3, and 4 show details of the boat and how it is put together.

The patterns can be enlarged to proper size, folded on the dotted lines, and put together for the various parts. On the toy here I have used a short metal lever, T, and trigger, as you can see, with a guide to hold it close to the frame of the submarine, but in Figure 3 I show how this trigger can be made of wire with a staple to hold it in place and a handle on one end for a pivot. By its own weight the flat part of this wire will drop into the notch N, of the dump pan, and hold it from upsetting.

This dump pan pivot s on a wire running through the holes H, and out through little tin-bearing pivots S, shown in the drawings in Figure 4.

These are made of tin cut to shape with an old pair of scissors.

A study of the drawings will tell you more than words, but if you want some fun, make some of these submarines and see which can dive the deepest and still come to the surface again.

And, by the way, by timing this toy with a stopwatch to a ten-foot depth and using this as a standard of comparison, then you can tell how deep any part of the lake is by noting the time it takes your submarine to go down to the bottom and come up again.