A shallow aluminum pan or serving tray filled with water, can be mounted on a three-sided masking base 4 or 5 in. high, so that miniature wooden boats can be maneuvered in the same mysterious manner in which the airfield vehicles were motivated in a preceding section. But be sure that the lake or harbor is of aluminum, not tin, or the magnet's magic power will fail to penetrate. Furthermore, because of the water, the three-sided base should be carefully dimensioned and solidly butt jointed, to prevent tipping and spilling.

The easiest way to make the small wooden boats "attractive" to the unseen magnet, is to stud their bottoms with a line of unpainted, metal thumb tacks. Profiles A and B, suggested in Figure 4.24, are warlike in character because it is anticipated that the young Admiral in charge of magnetic control will suffer initial accidents, which will promptly suggest planned collisions and rammings. To this end half of the Navy may be painted a different (enemy) color; otherwise they would receive a uniform battleship gray with black guns and funnels. For peaceful pursuits, or to provide non-combatant vessels for convoying practice, a stylized freighter and ocean liner are included in C and D. All four types of vessels can be whittled from soft pine, or may be built up in layers, if preferred.

If the game catches on and the aluminum tray is large enough, two or even three edges can be enclosed in a narrow ridge of cement or well-shellacked plaster of Paris "land," roughened on top and painted green or brown, to form an atoll or land-locked harbor. Insert a tubular lighthouse before the cement or plaster hardens, as well as small storehouses, quarters and offices, as per instructions from the Base Commander. The squared tray available in the writer's home measures 1 in. deep and 14 in. by 17 3/4 in., which will fit into the harbor shown in Figure 4.22.

Fig. 4.24. Deepsea vessels.