Product Description: You will be buying a Photograph produced using professional photographic lab equipment and printed on high quality photographic paper. Please note that sometimes a small amount of image cropping is neccessary to produce your photograph. Produced on a Print & Supply basis from an image hosted on Geograph

Condition: New

Size: 6" x 4" - 150mm x 100mm

Copyright (Photograph and text in Photograph Notes): � Copyright Chris Allen and licensed for reuse under creativecommons.org/licenses/by-sa/2.0 details available here: https://creativecommons.org/licenses/by-sa/2.0/

Photograph Notes: A detailed view of one of the two Hathorn Davey horizontal compound non-rotative 'differential' pumping engines built in 1894. This complex looking piece of machinery is known colloquially as the 'steam man' and control the engine's slide valves. It controls both the speed at which the engine strokes and the pause between strokes. The control of the speed is as a result of the differential between a fixed speed (provided by the steam man operating against a water cataract) and a variable speed (the engine's piston speed that varies with the load or changes in the load on the pumps). It is this differential that gives this type of engine its name - the differential engine.

Postage & Packing: All items are posted securely packaged with card inserts to avoid damage in the post hence the higher postage cost than the standard cost of a 1st / 2nd class stamp. We discount postage for multiple photographs and slides purchased, please wait for the invoice to be sent with the discounted postage rate applied.