Brunel's tunnelling shield. This three-tiered frame was proposed by Sir Marc Isambard Brunel (1769-1849) in 1823 for use in the construction of a tunnel beneath the river Thames, London, England. Two plans of the tunnel are seen at top and upper centre. This shield consists of 11 frames, each split into 3 compartments, that could be edged forward independently. The frames support the tunnel sides while allowing excavators and bricklayers to work from within them. When tunnel construction began in 1825 a 12-frame version of the shield was used. The Thames tunnel, which ran between Rotherhithe and Wapping, was completed in 1873. Engraving taken from Mechanics Magazine (27th September 1823).