WHEN Diver Dan is at work, children -and grownups too-watch spellbound. This robotlike figure sinks into the water, remains out of sight for a time, and mysteriously emerges, only to repeat the performance a few seconds later. "How does he do it?" is the inevitable question.

For all his mystifying behavior, the diver is easy to make. Pry off an end of a tall evaporated-milk can, heating it to melt the solder. Cut a 1" hole in this end and solder in a perforated tube bent from scrap tin plate, as shown in the drawing. Attach iron-pipe legs and wooden feet with long bolts and nuts.

Solder shut any holes in the top of the can; then punch a clean 1/4 " hole in the center from the inside. To a piece of wire, solder an acorn nut; insert the wire in the 1/4" hole and push on a 1" cork as shown. Cut off one end of a smaller can and make a hole in the other, as well as two small holes for eyes. Solder this can, open end down, to the top of the larger can. Be sure to punch a small hole near the joint as indicated in the drawing.

Replace the bottom of the tall can and "tack" it on with solder. Finally, solder on tin-plate tubes or wooden dowels with wire or metal ferrules as arms.

To put Diving Dan to work, drop a small piece of dry ice (solid carbon dioxide) through the trap in the bottom, and tilt the can so that the piece falls back inside. Use tongs in handling dry ice-never touch it with the bare hands, for it can cause a serious burn. When dropped into water a few feet deep, the diver promptly sinks, but the cork then rises, shutting the air valve. Gas given off by the dry ice is thus trapped, and drives out the water, bringing the diver again to the surface. Above water the cork drops; the gas escapes, water enters again, and the cycle is repeated. Dry ice must be used; ordinary ice will not do.

If the diver does not rise, cut the legs somewhat shorter to lighten them. It is a wise precaution to attach a cord "life line" by which Diving Dan can be rescued if the dry ice gives out and leaves him stranded at the bottom of the lake.

If the diver does not risecut the legs somewhatlife line