CHAPTER XX.

THE WATT AND THE TREVITHICK ENGINES AT DOLCOATH.

Early steam-engines--Semicircular boiler, 1775, net power 7 lbs. on the inch--Watt's statement in 1777--Engines in Dolcoath--Watt's engine, 1778--Watt's engine at Herland, 1798--Trevithick's tubular boiler, 1799--Reconstruction of the Carloose 45-inch, 1799--Gross and net power of engines--Comparison of Newcomen, Watt, and Trevithick engines--Boiler explosion, 1803--Strong rivalry with Watt--Locomotive at Coalbrookdale, 1803--Watt's proposed locomotive--Competition in Wales--Numerous high-pressure engines, 1803--Patent difficulty--Watt's opposition, 1804--Government inquiry--Competitive trials in Wales--Tramway locomotive, 1804--The bet--Opposition because of saving of labour--Worcester engine--West India Docks engine--High-pressure steam condensing engines--One or two cylinders for expansion--Sirhowey boilers--Mr. Homfray's opinion of the Watt opposition--Mr. Whitehead makes engines in Manchester--Cylindrical tubular boiler in Wales for large engines, 1805--Watt contests at Dolcoath, 1805--Steam-blast--Superiority of high-pressure whim-engines--Proposed boiler for the large pumping engine, 1806--Steam pressure--The Watt boiler--Comparison of size of fire-place and coal used--Dredger contract--Theory of steam--Trevithick's Dolcoath boiler when applied to the Watt engine, with expansive gear, to save 300l. monthly, 1806--Momentum of pumping engine--Continued tests of high and low pressure whim-engines at Dolcoath--Watt engine put aside, 1806--High-pressure engines ordered, 1806--High-pressure pumping engine for Wheal Abraham, 1806--Disputed patent right--Expansion reduces heat--Boiler for the Watt 63-inch engine, 1806--Cost of Trevithick's boiler--Advantage of small tubes in boilers--Trinity Board--Watt's steam-cylinder unsuitable for high steam, 1806--Sims' trial of engines--Little fight--Tubular boilers, 1806--High-pressure steam pumping engines, 1818--Reporter of engines--Application to Government, 1810--Dolcoath engines and boilers--High steam to the Watt engine--Duty of engines, 1812--Watt's boiler thrown out--Expansive valve--Dolcoath manager--Saving by boilers and expansive working, 1812--Lean's reports--Increased duty of the three old Dolcoath engines, 1814--76-inch engine, 1816--80,000l. a year saved--Durability of engine--Its removal--Cylindrical boilers--Hornblower and Watt engines--Davies Gilbert's report, 1798--Lean's report, 1816--Watt's views of expansive working--Watt's steam of 1 or 2 lbs. to the inch--Pole's statement--Engine at Marazion, 1804--Woolf in Cornwall--Rees' Cyclopædia--'Encyclopædia Britannica'--Application to Parliament--Wheal Towan--Newcomen and Watt engines--Pompe-à-feu 'La Belle Machine,' Dolcoath Page 114-194