Construction of tunnel under the Hudson river, between NY and Jersey City. 1) Cutting edges of the shield, 2) tunnel and hydraulic shield, 3) Interior tunnel and hydraulic shield. A tunnelling shield is a protective structure used in the excavation of tunnels through soil that is too soft or fluid to remain stable during the time that it takes to line the tunnel with a support structure of concrete, cast iron, or steel. In effect, the shield serves as a temporary support structure for the tunnel while it is being excavated. In 1888 a British company that employed James Henry Greathead as a consulting engineer attempted to resume work on the Hudson tubes, but they too were unsuccessful in completing them and were also out of funds by 1891. The Uptown Hudson Tubes are a pair of tunnels that carry PATH trains under the Hudson River between Greenwich Village in New York City, New York and Jersey City, New Jersey. Illustration appeared in "Scientific American", November 1, 1890.