the coalfields until the early decades of the nineteenth century. By 1729, when Newcomen died, his engines had spread to France, Germany, Austria, Hungary and Sweden. A total of 110 are known to have been built by 1733 when the joint patent expired, of which 14 were abroad. In the 1770s, the engineer John Smeaton built some very large examples and introduced a number of improvements. A total of 1,454 engines had been built by 1800. James Watt's steam engines A fundamental change in working principles was brought about by James Watt. With the close collaboration of Matthew Boulton, by 1778 he had succeeded in perfecting his steam engine which incorporated a series of radical improvements; notably, the use of a steam jacket around the cylinder to keep it at the temperature of the steam and, most importantly, a steam condenser chamber separate from the piston chamber. These improvements increased engine efficiency by a factor of about five, saving 75% on coal costs. The Newcomen engine could not, at the time, be easily adapted to drive a rotating wheel, although Wasborough and Pickard did succeed in doing so in about 1780. However, by 1783 the more economical Watt steam engine had been fully developed into a double-acting rotative type with a centrifugal governor, parallel motion and flywheel, which meant that it could be used to directly drive the rotary machinery of a factory or mill. Both of Watt's basic engine types were commercially very successful. By 1800, the firm Boulton & Watt had constructed 496 engines, with 164 driving reciprocating pumps, 24 serving blast furnaces, and 308 powering mill machinery; most of the engines generated from 5 to 10 hp. An estimate of the total power that could be produced by all these engines was about 11,200 hp. This was still only a fraction of the total power-generating capacity in Britain by waterwheels (120,000 hp) and by windmills (15,000 hp); however, water and wind power were seasonably variable. Newcomen and other steam engines generated at the same time about 24,000 hp. James Watt invented the steam engine in 1770. Development after Watt The development of machine tools, such as the lathe, planing and shaping machines powered by these engines, enabled all the metal parts of the engines to be easily and accurately cut and in turn made it possible to build larger and more powerful engines. In the early 19th