Geograph - photograph every grid square

Built in 1795 and although much rebuilt is still considered the world's oldest in situ atmospheric steam engine. The engine has been restored and is now worked hydraulically. Although this view lack depth of field below the floor grating it does show the top of the hydraulic power system that is connected to the bottom of the plug rod and moves the engine via the parallel motion attached to the replacement cast iron beam (the 1795 beam would have been wooden). This cylinder replaced a small pump that would have fed the injection water cylinder and is now in the corner of the engine house. The hydraulic power pack is housed in a more modern electric pump and fan house that replaced the Newcomen engine. The electronic controller gives a 'soft' start to minimise shock loadings and then moves the engine with a faster indoor stroke and a slower outdoor stroke, mimicking how it would have worked but apparently at about half speed. The operator uses a hand held remote to start and stop the engine while keeping a close eye on the visitors. Visitors are all guided to one floor at a time with the engine static and it is then started when the guide has confirmed nobody is going to be struck by the motion. This allows the use of a minimum of guarding and helps to retain the atmosphere of this Scheduled Ancient Monument.