The old engine houses are the most iconic remains of Cornwall’s industrial past.
They were built, largely in the 19th century, to house the steam engines that powered the machinery vital to mineing.
If you make a hole in Cornwall it will soon fill up with water. Steam pumps were introduced in the early eighteenth century. This technology culminated in the development of the Cornish high-pressure steam-pumping engine in the nineteenth century. The engine houses that once contained these engines stand close to the mine’s principal shafts.
Engine houses often come as pairs. In one would be the engine that powered the pumps. The other engine would run the hoisting and crushing machinery.
Most surviving engine houses are rectangular with one much thicker wall in the front (the bob wall), this was constructed using more massive stones, often cut granite, and was perhaps two-thirds of the height of the other walls. This wall supported the beam (known in Cornish mining as a bob) which transmitted the motion of the piston to the pump rods in the shaft or to the hoisting or crushing machinery. This wall had to withstand both the weight (that might be over 50 tonnes for a large pumping engine) and the rocking forces of the bob.
The other walls braced the bob wall and helped to take some of the working stresses of the engine. The rear wall contained the cylinder opening through which the cylinder, bob, and other large components were brought into the engine house. There were usually three chambers internally. Chimney stacks were either built-in to a rear corner of the engine house or sometimes detached and connected by a flue.