Volume Six - Pre-Victorian to the Present Day - Select Aspects - The subway under the river Ely story . . .

Later this chamber was made further water resistant by admitting compressed air. So, it sounds like the chamber employed at the Ely subway was a direct descendent of Mr. Greathead's design with links all the way back to Mr. B himself.

A photograph of the steam driven air compressor mounted at the surface which supplied the air used in the construction of the River Ely Subway.   It probably applied a pressure of about 15 to 25 pounds per square inch (p.s.i.) to the working shield area to limit the ingress of water to the workings, but, this pressure was probably adjusted to suit the state of the tide being at its highest pressure at Spring tides.

James Henry Greathead (1844-1896) was of South African descent and was a mechanical and civil engineer renowned for his experience and development of procedures and equipment for tunneling work, the principle of which is still used in modern tunnel construction.