The atmospheric engineThomas Newcomen, ironmonger of Dartmouth · first erected 1712
The first steam engine that earned its keep, built to pump the flooded coal and tin mines that were defeating horse-driven gins. Its trick is humility: the steam never pushes — it is condensed by a jet of cold water, and the weight of the atmosphere shoves the piston into the vacuum. Strengths: magnificently simple, tolerant of village blacksmithing, and nearly unbreakable — some ran for a century. Weaknesses: the cylinder is chilled at every stroke and must be re-heated at every stroke, so it devours coal for a fraction of one percent of its heat returned as work; it only nods, never turns, so it can pump and do nothing else. Set the injection water against the coal it costs, and deepen the mine until the atmosphere itself gives up — the two levers that ruled its whole working life.
Key to the plate
a. — the great beam. An oak rocking beam, the largest timber in the county, balanced on the engine-house wall. The cylinder pulls one end down; the pump rods pull the other. Nothing rotates — the engine simply nods, a dozen times a minute, for decades.
b. — chain & arch head. The beam ends in curved arch heads, and chains ride their arcs. A chain can only pull — which suits an engine whose working stroke is all one way: steam merely refills the cylinder; the atmosphere does the pulling.
c. — injection cistern. Cold water standing ready overhead. Sprayed into the steam-filled cylinder, it condenses the steam to a near-vacuum in a heartbeat, and the weight of the sky pushes the piston down. Too little spray and the vacuum is poor; too much chills the cylinder and wastes the next filling — the whole economy of the engine hides in this cock.
d. — haystack boiler. A copper dome no stouter than a brewer’s kettle, set in brick over the fire. It bears scarcely two pounds of steam — and needs no more, for the steam only breaks the vacuum and refills the cylinder between strokes. The power comes from the atmosphere, not the boiler.
e. — mine shaft & pump rods. The customer. Wooden rods hang down the shaft to lift water from the workings, a fathom or so per stroke. Their weight pulls the beam over for the refilling stroke — the engine and its load take turns doing the work.