142 THE WATT AND THE TREVITHICK ENGINES. 



" MR. GlDDY, " CAMBORNE, February 18th, 1806. 



" Sir, On my return from town I altered the pressure 

 of the steam-engine at the bottom of the hill, Dolcoath. Before 

 I returned there was a trial between mine and one of Boulton's ; 

 both engines in the same mine and drawing ores from the same 

 depth. The result was, Boulton's beat the pressure-engine as 

 120 to 55. Since it was altered there have been three other 

 trials ; the result was 147 to 35 in favour of the pressure of the 

 steam-engine. They are now on trial for another month, and at 

 the next account they intend to order a new boiler for the great 

 engine, and work with high-pressure steam and condenser, pro- 

 vided this engine continues to do the same duty as was done 

 in the former trials. This engine is now drawing from a per- 

 pendicular shaft, and Boulton and Watt's from an underlay 

 shaft ; but to convince Captain Jos. Vivian, we put it to draw 

 out of the worst shaft in the mine, and then we beat more than 

 three to one ; we lifted in forty-seven hours, 233 tons of stuff 

 100 fathoms with 47 bushels of coal. The engine was on trial 

 sixty-six hours, but nineteen hours were hindered by the shaft 

 and ropes, &c., which made the consumption of coals about fths 

 of a bushel per hour. The fire-tube is 2 feet 3 inches diameter, 

 and the fire-bars were only 14 inches long. The fire-place was 

 but 2 feet 3 inches wide by 14 inches long, and the fire about 

 4 or 5 inches thick ; it raised steam in plenty ; it was as bright 

 as a star. The engine is now doing the work of two steam- 

 whims ; the other steam-whim in the Valley is turned idle, 

 and both shafts will not more than half supply it. 233 tons 

 are equal to nearly 2000 kibbals, which were drawn in forty- 

 seven hours. 



" Mr. Harris has a 12-inch cylinder making at Hayle, for 

 Crenver, and Mr. Daniel has a 14-inch for Perran-sand, and 

 a great number are waiting for the trial of this month, before 

 altering their boilers to the great engines. 



" The steam-whim that is now turned idle at the Valley was 

 13^-inch cylinder, 4-feet stroke ; it turned the whim one revo- 

 lution to one stroke, and lifted the kibbal the same height at a 

 stroke as my engine did, and I think took the same number of 

 gallons of steam to lift a kibbal as mine did. Their steam was 



