Cartesian Devil, DIVER — Chambers's Encyclopaedia

Cartesian Devil, DIVER, or BOTTLE IMP, is a scientific toy named after Descartes. A tall glass vessel is nearly filled with water, and covered with an air-tight piece of bladder or india-rubber. In and on the water floats a small hollow figure, with a hole near the top, partly filled with air and partly with water. When the cover of the glass is pressed, the air beneath is compressed and water enters the floating figure (so as to bring the air in it to the same degree of compression), and the figure sinks in the water, not rising again till the pressure is removed.—For the CARTESIAN PHILOSOPHY, see DESCARTES.