THE WATT AND THE TREVITHICK ENGINES. 193 



180(), recommending a cylindrical boiler for the Dol- 

 coatli pumping engine, because similar boilers giving 

 steam to his whim-engines have enabled them to beat 

 the Watt whims. This continued until 1810, when the 

 greatly - increased power and economy of the high- 

 pressure expansive steam pumping engine at Wheal 

 Prosper caused the neighbouring Dolcoath in 1811 to 

 give Trevithick's plans free scope. The long smoulder- 

 ing rivalry between low and high pressure, on the eve 

 of the final discomfiture of the former, burst forth in 

 loud words and evil prognostications, causing the 

 mining interest of Cornwall to appoint an examiner 

 who should publish monthly the duty performed by the 

 various pumping engines, the first of which appeared in 

 the autumn of 1811, when Trevithick was building his 

 boilers in Dolcoath, and preparing the engines, as far as 

 was possible, to submit to strong steam. By expansive 

 valves and suitable gear, balance of power between the 

 engine and the pump-work necessitating balance-bobs, 

 strengthening the pit-work to bear the more powerful 

 and sudden movement, and fifty other things, which 

 we know must have presented themselves in such 

 work, occupied the greater part of Trevithick's time 

 from 1811 to 1814. That first report enumerates 

 twelve pumping engines, probably all of them Watt 

 engines, averaging a duty of seventeen millions. 



We have before traced the rapid and immense 

 increase in the power and in the duty of Cornish 

 pumping engines from 1811$ and it may be taken as 

 comparatively true in the larger sense applying to the 

 improvement of the steam-engine everywhere. 



Dolcoath Mine, one hundred years ago, under the 

 management of Trevithick, sen., followed by his son as 

 the strong-steam engineer, and by his grandson as one 



VOL. n. o 



