Traditional tin-plate toy powered by the World’s smallest steam engine.
The two tubes seen in the base of the hull are filled with water. The small frying-pan like gadget then has a piece of candle wax placed in it which is melted over a flame and a small wick (cut from the ‘string’) inserted and lit. The flame is then placed under the small metal boiler (the small grey bit) and the resultant expansion as the water in the tubes turns to steam and subsequent contraction as more water is drawn in, propels the boat. The distinctive sound of the expansion and contraction gives the toy its name.
This one was purchased at the London Model Engineer exhibition at Alexandra Palace in January. The chap that makes them uses the proceeds to restore an old water-mill in Cumbria.