"Sir,--I have your favour of the 27th February, and requested Mr. Page to send to you a sketch of the agreement. On seeing him yesterday, I found that he had neglected to send it to you. He will leave the country for London in a few days, and intends to call on you at Dolley's as soon as he arrives. I do not know that the agreement matters much for a few days up or down. The terms are well understood between us, which is that the adventurers and I equally share the advantages that may arise from this new engine over Boulton and Watt's. When you have fully arranged with your adventurers about the engine, please to write me, and I will immediately proceed to order the engine; and in the interim the agreement will be drawn up by Mr. Page, and executed either here or in London, just as may suit. "I remain, &c., "R. TREVITHICK. "P.S.--Herland engine goes on better and better. Your adventurers will get a satisfactory account by applying in town to Mr. Wm. Phillip, No. 2, George Yard, Lombard Street. He is the principal of the London adventurers." Trevithick believed that mine adventurers would agree to pay him one-half the saving caused by his engines, as compared with the cost of fuel in the Watt engine. The duty performed by the latter was understood and agreed to generally; persons were chosen by the adventurers to experiment and report on the duty of Trevithick's pole-engine, that the amount of payment might be ascertained in proportion to the saving effected. "MR. GIDDY, "PENZANCE, _April 2, 1816_. "Sir,--I have long wished to write to you about the Herland engine, but first wished to see the engine loaded with a second lift, and a trial made of the duty. Yesterday was fixed on, before ordering another engine for the eastern shaft. "The persons attended. The arbitrators gave the duty as forty-eight millions, and said they had no doubt the engine would perform above sixty millions before getting to the bottom of the mine. "They were much within the duty, but I did not contend with them, as they said it was quite duty enough. "The engine worked 9-1/4 strokes per minute, with 2 bushels of coal per hour for the whole time, 10-feet stroke. There were two pump-lifts of 14-1/2-inch bucket, making 43 fathoms, and 26 fathoms of 6-inch for house-water. "The steam was from 100 to 120 lbs. to the inch. The valve open while the plunger-pole ascended 20 inches, then went the remainder of the 10-feet stroke expansive. "It went exceedingly smooth and regular. Some time since, by way of trying the power of the engine, we disengaged the balance-bob. The engine worked twenty strokes per minute, with 17 tons of rods, &c., and drew 14-1/2-inch bucket 23-1/2 fathoms, and a 6-inch bucket 26 fathoms, 10-feet stroke, twenty strokes per minute.