Provide a glass tube about three feet long and half an inch in diameter; nearly fill it with water, upon the surface of which pour a little colored ether; then close the open end of the tube carefully with the palm of the hand, invert it in a basin of water, and rest the tube against the wall. The ether will rise through the water to the upper end of the tube; pour a little hot water over the tube, and it will soon cause the ether to boil within, and its vapor may thus be made to drive nearly all of the water out of the tube into the basin. If, however, you then cool the tube by pouring cold water over it, the vaporized ether will again become a liquid, and float upon the water as before.