THE WATT AND THE TEEVITHICK ENGIXKS. 167 



two or three years to forty-eight millions, being three 

 times the duty performed by the Watt 63-inch double 

 engine before it was supplied with steam from Trevi- 

 thick's boilers, and twice as much as it performed when 

 so supplied. Lean says, " This was the first instance of 

 such duty having been performed by an engine of that 

 simple construction." The other mines followed Trevi- 

 thick's advice, but never paid him a penny. On this 

 Lean again says, " The engines at work in the county in 

 1835 would have consumed 80,OOOZ. worth of coal over 

 and above their actual consumption yearly, but for the 

 improvements that had been made since 1814." 



Trevithick's engines were very durable, as well as 

 cheap in first cost and in working expense. This 

 famous Dolcoath 76-inch engine remained in constant 

 work night and day for fifty-four years ; after which 

 good service the steam-pipes, being thinned by rust, 

 were held together by bands and bolts ; the steam-case 

 around the cylinder would no longer bear the pressure 

 of steam ; the interior of the cylinder from wear was one 

 inch larger in diameter than when first put in, and had 

 to be held together by strap-bolts. The original boilers 

 were said to remain, only they had been repaired until 

 not an original plate remained ; but there they were in 

 the old stoke-hole in 1869, when, from the fear of some 

 part of the engine breaking and causing accident, it 

 was removed. 



In 1867 the writer was a member of the Dolcoath 

 Managing Committee, when it was determined that the 

 old engine of 1816 should be replaced by a new one. 

 The cylinder sides were reduced in thickness by half an 

 inch ; the steam-pipes and nozzles were thinned by rust 

 and decay; the valves and gear- work remained in good 

 order. Captain Josiah Thomas, the present manager of 



