The Boiler House, excavated in 2013 in advance ofdevelopment of the northern site of Leigh Gunpowder Mills. From the report:

"The Boiler House, excavated as Area 2 here and first seen in evaluation trenching, was very well preserved, represented by a bank of four furnaces with firemouths to the river, flues oriented northwestwards Three original flues were located, all of the same character, with polygonal firemouths next to wide stoking chambers. One stoking chamber had a brick floor, two others had been covered with a concrete screed. The flues were constructed with firebricks for floor and base, and although they were lightly discoloured, had clearly held up well to heat...

A second major part of the building was a smaller square building at the southwest end. This appears to once been partially below ground, later infilled with concrete, to form a base for a massive piece of plant with a cruciform mount. This block is a good candidate for power transfer across the river to the mills, providing power either through steam powered hydraulics, or through rotary power of a wheel powered by the boilers, or perhaps both. The deep chamber may have held a wheel or sequence of wheels, perhaps later raised above ground on a new mount.

Just east of the building, a contemporary well or cistern was recorded. This could have been for drawing water to top up the boiler system, or to deal with uncontrolled fires." (1)

"What is not clear from the archaeological record is the character of the power provided: whether it was rotary power transmitted by shafts and wheels, or pistons powered by steam, with the steam piped across the river." (1)

<1> AOC Archaeology, 2015, Gunpowder Mills, Leigh, Tonbridge, Kent, A Post-Excavation Assessment (Unpublished document). SKE31577.