This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
The device illustrated has for its object the production of power in small quantities with little attention and no expense. All that is needed to produce the power is common ordinary water, and the device will continue to operate until the amount of water placed in the receptacle has evaporated.
The device consists of a rectangular vessel provided with legs and a cover.
Each end of the vessel is provided with an opening, A, adapted to receive and hold in place plaster-of-paris cups, B. The part extending into the tank is provided with a wick, C, which reaches to the bottom of the vessel. A glass tube, D, is provided with a bulb on each end and partly filled with alcohol, the remaining space being exhausted of air. The glass tube is secured to a hanger which is pivoted to the bottom of the vessel.
After a quantity of water has been poured into the vessel and the device allowed to stand undisturbed for a few minutes, the tube will begin to move with an oscillating motion. Some of the water in the vessel has been conducted by means of the wicks C to the bent plaster cups, from the surface of which it evaporates, thus absorbing latent heat and producing a lower temperature in the cups than that of the surrounding atmosphere. The bulb in contact with the cup thus acquires a lower temperature than the one at the end D, which will result in condensation of the alcohol vapor within the former. The pressure of the vapor in the lower bulb will then force the alcohol up the inclined tube into the higher bulb, the evaporation in the lower bulb maintaining the pressure 'herein
When a sufficient quantity of alcohol has been forced into the upper bulb, it will descend, and thus elevate the other bulb into its cup. The phenomena just described will be repeated in this bulb and the oscillation will continue until the water in the vessel has been absorbed and evaporated. - Contributed by E. W. Davis, Chicago.
Ill: Details of the Engine