108 POLE STEAM-ENGINE. 



sumption of coal by those two particular inventions, 

 twenty-six millions of pounds of water raised one foot 

 high by a bushel of coal of 84 Ibs., being the duty of the 

 best Watt engines, to be taken as a starting-point for the 

 payment. Treskerby and Wheal Chance paid for the 

 pole-engine, but the Trevithick boilers suitable for high 

 steam, and the simple methods of working it expan- 

 sively, had been made so generally public, that people 

 professed to think they had a right to them, when but 

 a few years before they had thrown the inventor off his 

 guard by saying " everybody knows that the Cornish 

 boiler is your plan, and as it cannot be denied, a 

 patent will be of no service." 



Mr. John Williams l stated " that whatever other 

 mines might do, he would insist, as long as he was 

 manager for Treskerby and Wheal Chance, the agree- 

 ment made should be carried into effect." The Wil- 

 liamses paid to Trevithick 300/. for the saving of 

 coal by the pole patent engine, as an " acknowledg- 

 ment of the benefits received by us in our mines;" 

 but no payment was made for the greater invention 

 of the high-pressure steam-boilers then in general 

 use. 



In 1814 the Watt Treskerby engine did seventeen 

 and a half millions. Trevithick's boiler and pole were 

 applied, and the duty was increased to more than forty 

 millions. In 1816 the same changes were made in 

 Wheal Chance, and the duty rose to more than forty-six 

 millions. The consumption of coal was reduced to one- 

 half, amounting in round numbers to a gain of 500. a 

 month in those two mines alone. 



1 Mr, John Williams had the remarkable dream, many hours before the 

 event, enabling him to describe the particulars of the assassination of Perceval 

 in 1812. 



