
A synopsis of the operation of the "drinking bird", a seeming perpetual motion machine, which, once put in contact with the water, will continue to bob up and down until it runs out of water, owing to a cooling effect of water (cold body) on the volatile methylene chloride CH2Cl2 vapor (working body), thereby turning the vapor back into liquid, and readjusting the gravitational balance of the bird, making it go into the vertical position, after which the head dries, more vapor evaporates into the head, the process starts over again

A synopsis of the operation of the "drinking bird", a seeming perpetual motion machine, which, once put in contact with the water, will continue to bob up and down until it runs out of water, owing to a cooling effect of water (cold body) on the volatile methylene chloride CH2Cl2 vapor (working body), thereby turning the vapor back into liquid, and readjusting the gravitational balance of the bird, making it go into the vertical position, after which the head dries, more vapor evaporates into the head, the process starts over again

In thermodynamics, drinking bird, or "dipping bird", is a fluid filled vessel, hinged near its midpoint, with a bird's head at its top and feathers near its bottom, that will do work, i.e. bob up and down, for days on end, via heat differentials and evaporation effects.

History
The drinking bird was invented in the 1940s by American chemist Miles Sullivan, patented by him in 1945, after watching bubbles go up a colored tube on a jukebox machine, and thinking about how much energy was lost by that process. [1]

Overview
The famous thermodynamic toy the “drinking bird” is an amusing toy, the thermodynamical operation of which notoriously baffled German-born American physicist Albert Einstein in 1946.

The dipping bird is a loose example of “thermodynamic art”, being a sort of atmospheric heat engine, which will run for days operating on the principle of heat loss via evaporation conjoined with the conversion of heat into work in the working body (liquid-vapor mixture of methylene chloride CH2Cl2) of the engine via the mechanical equivalent of heat.

The operation of the drinking bird is similar, in a way, to Greek inventor Hero of Alexandria’s first century AD rotating toy steam engine the "aeolipile", a heat-driven spinning steam ball.

References
1. (a) The Father of Inventions - by Anne Sullivan.
(b) Interview of Miles Sullivan - by reporter Holly Doyle of WWMT, Kalamazoo, Mi, March 14, 2006.

Further reading
● Modell, Michael and Reid, Robert C. (1974). Thermodynamics and Its Applications in Chemical Engineering, (pg. 92). Prentice-Hall.
● Lorenz, Ralph. (2006). “Finite-time Thermodynamics of an Instrumented Drinking Bird Toy”, American Journal of Physics, Vol. 74, No. 8, August.