Geograph - photograph every grid square

An atmospheric mine drainage engine built in 1795. The power stroke was made under atmospheric pressure and the steam pressure in the cylinder was at best little more than atmospheric. Therefore it was possible to have an open topped cylinder with steam below the piston and the atmosphere above it. Sitting on top of the piston would have been a few inches of water to help provide a seal - along with rope packing around the edge of the piston held in place with a junk ring. The cylinder bell mouth contains the water on top of the piston and there is a hole in it that leads to the overflow. A green water feed pipe is seen on the right just below the top edge. The piston and its junk ring are visible in the cylinder.

Although many people have never heard of this site it is very important - the only in situ Newcomen atmospheric engine in the world!