Watt's separate condenser, second model, 1765.
© Science Museum / Science & Society Picture Library
James Watt (1736-1819) fundamentally improved steam engine design with his separate condenser, which he patented in 1769. Early Newcomen engines were inefficient as their working cycle entailed continual heating and cooling of the cylinder, which wasted fuel. The separate condenser meant the steam was condensed in a separate chamber, allowing the cylinder to be kept hot and greatly increasing fuel efficiency. This model was probably made immediately after the first but Watt seems to have quickly forgotten about it. It was preserved not in his garret workshop but on the premises of James Watt & Co. It is more elaborate than the first model but was probably les succesful.