178 THE WATT AND THE TREVITHICK ENGINES. 



striking, and the public were careless of principles, the 

 one most puffed was most thought of; but the money 

 saved was tangible, and in 1815 a special trial was 

 made, which lasted two days, to discover if it was really 

 true that Trevithick's appliances could so increase the 

 duty of the engine. The 63-inch cylinder, then called 

 Stray Park engine, was selected ; the result proved that 

 the large saving reported from Trevithick's boilers and 

 expansive working during the last three or four years, 

 was an incontrovertible fact. 



The high-pressure steam was also given to the de- 

 feated Watt 63-inch double engine ; yet this newest of 

 the three engines was the first to be condemned, and 

 her place was taken in 1816 by an engine of 76 inches 

 in diameter, which Trevithick promised should, with 

 his high steam and new expansive gear, do the work 

 of the Watt 63-inch and the old 45-inch put together; 

 which was more than fulfilled by its doing forty mil- 

 lions, and, as Lean says, " was the first instance of such 

 duty having been performed by an engine of that simple 

 construction." 



In 1819 the new 76-inch engine which had been 

 erected by the mine engineers, Jeffrie 1 and Gribble, who 

 had long been employed by Trevithick in Dolcoath, 

 was the best in the county, doing forty-eight millions, 

 nearly three times the duty as given by Mr. Gilbert for 

 the Watt engine in 1798. In 1827 Trevithick's pupil, 

 Captain Samuel Grose, erected his Wheal Towan engine, 

 which performed a duty of eighty-seven millions, some 

 of the working drawings of which were made by the 

 writer. In 1835 the principle laid down by Trevithick 

 hacl become so general in the county as to cause a saving 



See vol. i., p. 106. 



