Figure 15 - The side and plan elevations of the tandem, compound, condensing, hydraulic pumping engine built by Tannett, Walker & Co., of Leeds. [178]

Some clarification of terms used:-

Tandem = two engines side by side.

Compound = steam enters a small bore, high pressure cylinder first, does work and exhausts into a second cylinder, of larger bore and does further work prior to exhaust.

Condensing = Exhausted steam is cooled in the condenser back to water but in the process creates a partial vacuum which assist the exhaust of steam and increases the power output of the engine considerably.

Hydraulic = in this case the engine produces water at pressure to power the motions of the coal tips.