Plate taken from the 'Illustrated London News'. The tunnel beneath Mount Cenis utilised several innovative techniques, including the diamond core drill which was invented in 1863 by Rodolphe Leschot, a French engineer and used for drilling blast holes. Another new discovery used in the tunnel's construction was that natural sources of water can be used to compres and dischare air by letting the water under its natural presure enter and leave closed vesels, so alternately discharging and drawing in new supplies of air. Thus, the action is the same as in a blowing engine, the water taking the place of the piston.
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