Simple household ingredients are used to motivate the three elementary toys described below. The chemical reaction set up between camphor and water furnishes the seemingly inexhaustive motive power for the first two demonstrations. For successful operation of these camphor toys, however, it should be noted at the outset that absolute freedom from grease or oil is essential, both in the water and on the toys themselves. This includes invisible oil which may be deposited by the fingers.

Perpetual Dancer

An ideal bedside companion which will spin for days without ceasing is floated on a saucer of clean water. The spinning element consists of a medium sized cork sliced about 1/8 in. thick, through the circumference of which are thrust two fine needles at right angles to each other. Four small rectangles of cork about 1/8 in. thick are then thrust upon the protruding ends of the needles as in A, of Figure 7.8. Next, four small pieces of pure camphor are attached by means of sealing wax to the left edges of the cork rectangles. A small dancing figure cut from light paper can be fastened upright to the center of the circular axis cork by means of a fight needle.

Fig. 7.8. Chemical toys.

After the assembled whirligig has been placed on the surface of the water in the dish, it will continue spinning without stopping for three or four days, depending upon the size of the camphor slices.

Motor Boat

Using the same motive power, a small boat of thin wood or glazed cardboard, cut in the form indicated in Figure 7.8 B, will be propelled forward when a piece of camphor is placed in the hollow at the stern so that it will just touch the water when the boat is floated. If the camphor is arranged a little to one side to act as a rudder, the boat will sail around the basin or tub of water until the camphor is exhausted. A second boat with a toothpick mast and tissue paper sail can be either entered in the race, or started in the opposite direction for the sake of excitement.

Swimming Fish

Not an exciting toy, particularly for observers devoid of patience. However, it eventually becomes self-propelled, because of the expansion of a drop or two of olive oil in the round reservoir shown in Figure 7.8 C. The fish is cut from flat typewriter paper or newspaper, with a long canal through which the oil pushes its way. Eventually, if the fish is not too heavy, it will display a phlegmatic forward motion, which may induce the young scientists to cut out bodies of different sizes with tapering canals and varying reservoirs. When all else fails, the action of oil at sea in calming raging waters may be explained, if not demonstrated.