A Souvenir of Guantanamo Bay is a little desk top toy that features a figure of an unfortunate individual being repeatedly subjected to a water-boarding process.
It works on the same principle of the nodding bird toy, that repeatedly dips its head under water (see link), except instead of a bird
there is a little replica prisoner, attached to a pivoting board. The unfortunate figure is repeatedly and mysteriously water-boarded on a continuous basis. Here's how it works:
The figure's head is shrouded by a towel that holds and hides from view the necessary glass bulb containing a small amount of dichloromethane.
The tube extends nearly all the way down the inside torso of the figure, into the bottom bulb, concealed inside the twin booted feet.
This is an amended version of the wiki explanation of how the dipping bird works, but applied to the "Souvenir of Guantanamo Bay".
A Souvenir of Guantanamo Bay is a heat engine that exploits a temperature differential to convert heat energy to a pressure differential within the device, and perform mechanical work. Like all heat engines, "A Souvenir of Guantanamo Bay" works through a thermodynamic cycle. The initial state of the system is a figure with a wet head oriented vertically.
The process operates as follows:
1 The water evaporates from the towel on the head.
2 Evaporation lowers the temperature of the glass head (heat of vaporization).
3 The temperature decrease causes some of the dichloromethane vapor in the head to condense.
4 The lower temperature and condensation together cause the pressure to drop in the head.
5 The higher vapor pressure in the warmer base pushes the liquid up the neck.
6 As the liquid rises, the figure becomes top heavy and tips over.
7 When the figure on the board tips over, the bottom end of the neck tube rises above the surface of the liquid.
8 A bubble of warm vapor rises up the tube through this gap, displacing liquid as it goes.
9 Liquid flows back to the bottom bulb, and pressure equalizes between the top and bottom bulbs.
10 The weight of the liquid in the bottom bulb restores the figure to its vertical position.
11 The liquid in the bottom bulb is heated by ambient air, which is at a temperature slightly higher than the temperature of the figure's head.
If a small basin of water is placed so that the figure's head dips into it on its descent, the miniature towel will continue to absorb water and the cycle will continue as long as there is enough water in the basin to keep the head wet.
A Souvenir of Guantanamo Bay was rejected by the Prison Authorities as an idea they were unwilling to endorse.