TIIK WATT AND THE TREVITHICK ENGINES. 165 



manager of Dolcoath, and in youth the acquaintance 

 of Trevithick, states that the new high-pressure boilers 

 were made in the mine in 1811, and gave their first 

 supplies of strong steam to the three large pumping 

 engines in April, 1812, with such good effect that 

 the increasing water which had threatened to drown 

 the mine was speedily removed, and that with a saving 

 of nearly one-half of the coal before consumed. Prior 

 to their use Dolcoath Mine paid 1000. monthly for coal ; 

 but for the latter nine months of the year, in conse- 

 quence of the new boilers, the cost was reduced to 612. 

 a month. This saving in the pumping cost of one mine 

 crowned with success the high-pressure steam engineer, 

 who had been steadily gaining ground during his fight 

 of twelve or fourteen years on the battle-ground chosen 

 by Watt thirty-three years before. 



The low price of tin and copper, which caused so 

 many engines to cease working about the close of the 

 last century, had changed for the better, and the present 

 century opened with an increasing demand for steam 

 power. Trevithick's high-pressure portable engines had 

 worked satisfactorily for several years ; and as a means 

 of making public the relative duty performed by Cornish 

 pumping engines, and of solving conflicting statements 

 on the rival systems of low and high pressure steam, 

 it was determined that an intelligent person should 

 examine and give printed monthly reports of the amount 

 of duty done by the different engines, and in 1810 

 Captain Andrew Yivian was requested to take this work 

 of engine reporter in hand ; on his refusal it was 

 offered to Trevithick. In August, 1811, Mr. Lean 

 commenced such monthly reports, showing that the 

 duty of twelve pumping engines at the end of that year 

 averaged seventeen millions, exactly the duty done by the 



