150 THE WATT AND THE TKEV1THICK ENGINES. 



he preferred two smaller boilers, because small tubes 

 have an advantage over large ones, and are much 

 stronger. 



The whim trials high-pressure puffer against low- 

 pressure vacuum went on for another fortnight, when 

 high pressure, having done twice as much work as low 

 pressure, with an equal consumption of coal, the adven- 

 turers threw aside the work that had been made for 

 another Watt engine, ordering one in its stead from 

 Trevithick ; but they could not just then make up their 

 minds to place the Watt 63-inch pumping engine in 

 his hands. 



DEAR SiR, " CAMBORNE, May 30th, 1806. 



" I am very happy to find you have so far continued 

 your agreement with the Trinity gents, and think the bargain 

 is a good one. Must still beg leave to remind you not to proceed 

 to show what your engine will do till the agreement is fully 

 drawn up and regularly signed. 



"Dolcoath. agents, since they are informed of the accident 

 at the iron-works in Wales, of the engine Howing to pieces, have 

 requested me to have your opinion whether the old cylinder is 

 strong enough for the boiler of the intended new engine, or 

 whether you would recommend them to have a new one. Your 

 answer to this as soon as possible, as Mr. Williams and some 

 others are likely to make some objections. 



" Mr. Sims, the engineer, has published in the Truro paper, 

 that one of Boulton and Watt's engines at Wheal Jewell has 

 drawn more than a ton of ore over and above that drawn by 

 the Dolcoath engine from the same depth by a bushel of coal. 

 On inquiry I found they had only tried for twenty-two hours. 

 They said they left off with as good a fire as they began with. 

 This I argued was not a fair trial. They say they are now 

 on a trial for a month. 



" The little engine at Wheal Abraham does its duty ex- 

 tremely well. The particulars as to consumption of coal 

 cannot be fairly ascertained, as she has never been covered, 



