Engraving showing the mouth of the despatch-tube and a carriage, carrying mail, of the Pneumatic Despatch Company, Battersea, London. This was an experimental setup to test the design of the tube and related engines over a quarter of a mile of irregular ground. Once the carriage was in the tube, the door was shut and pneumatic pressure used to 'suck' the carriage through the tube. The company's intention was to link London's Post offices and railway stations with a network of underground pneum