Speed of sound experiment. Coloured historical artwork of an experiment to find out the speed of sound through water. The experiment, on Lake Geneva in Switzerland, involved two boats. Apparatus on the first boat (at left) enabled a bell to be rung underwater at the same time that a charge of gunpowder was ignited in the air above it. The time at which the bell was heard through the ear-trumpet attached to the second boat (at right) was noted. This was compared to the time at which the flash of gunpowder was recorded by a chronometer on this second boat. This gave a speed of about 1435 metres per second, or roughly four times the speed of sound through dry air.