Trevithick had desisted from securing a patent for the large high-pressure steam-boilers and expansive working, on a verbal understanding that he should receive one quarter of the saving from the reduced consumption 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 lbs., 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 expansively, 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[40] stated "that whatever other mines might do, he would insist, as long as he was manager for Treskerby and Wheal Chance, the agreement made should be carried into effect." The Williamses paid to Trevithick 300_l._ for the saving of coal by the pole patent engine, as an "acknowledgment 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. [Footnote 40: 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.] 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_l._ a month in those two mines alone. /# "TREVINCE, near TRURO, "DEAR SIR, _5th January, 1853_. "I am favoured with your letter of the 31st ult., enclosing also one from Mr. F. Trevithick, of the 24th idem, and have much pleasure in complying with your joint request to the best of my ability. I was well acquainted with the late Mr. Rd. Trevithick, having had frequent occasion to meet him on business and to consult him professionally; and I am gratified in having the present opportunity of bearing testimony to his distinguished abilities, and to the high estimation in which the first Cornish engineers of the day then regarded him. I need scarcely say that time has not lessened the desire in this county especially to do him justice. As a man of inventive mechanical genius, few, if any, have surpassed him, and Cornwall may well be proud of so illustrious a son.