This is a sketch design and description for a cloud chamber taken from Charles Wilson laboratory notebook.
The cloud chamber was a device for visualising subatomic particle tracks, using condensing water vapour within a sealed chamber. It was invented and developed by C.T.R. Wilson from 1911 and variations on the idea were widely used by particle physicists until the 1950s. This drawing, inscribed ‘March 18 1911’, is the very first description of the device and extracted from a notebook kept by C.T.R. Wilson in the period 1908-1912 which includes first detailed planning of Wilson's cloud track chamber.