Side view of Brunel's shield for boring the Thames tunnel. It consisted of 12 vertical cast iron sections, each divided horizontally into three cells and pivoting on a foot (A) The men were protected by a number of wooden poling boards (B) provided with small screw jacks (C). When the entire face had been excavated, all the screw jacks were released and the shield moved forward by means of master jacks (D) between shield and brickwork at roof and floor. Marc Isambard Brunel (April 25, 1769 - December 12, 1849) was a French Engineer. His greatest achievement was the Thames Tunnel, an underwater tunnel, built beneath the River Thames connecting Rotherhithe and Wapping. It measures 35 feet wide by 20 feet high and is 1,300 feet long, running at a depth of 75 feet below the river's surface. It was the first tunnel known successfully to have been constructed underneath a navigable river, and was built between 1825 and 1843. This image has been color-enhanced.