170 THE WATT AND THE TREVITHICK ENGINES. 



the 63-inch single engine, then called Wheal G-ons, the 

 latter in its original form of open-top cylinder atmo- 

 spheric ; shortly after which it probably received a 

 cover about the same time as the 45-inch, for both those 

 engines were thoroughly repaired by Trevithick at the 

 reworking of the mine, twelve or fourteen years prior to 

 the use of the cylindrical boilers. 



"At the time that Boulton and Watt made their trial of 

 Seal-hole engine against Hornblower's engine at Tin Croft, the 

 engines were put in the best order, and good coals brought in 

 for the purpose, to work for twenty-four hours. The trial was 

 attended by the principal mining agents ; the result was about 

 ten millions by each engine. 



" At Dolcoath Mine an old atmospheric engine continued to 

 work for several years by the side of one of Boulton and Watt's 

 engines of the same size ; the water lifted and coals consumed 

 were carefully taken and made known to the public, showing 

 that Boulton and Watt's engine performed, when compared 

 with the old engine, as 16 to 10." 1 



Hornblower was an active engineer in Cornwall 

 before Watt ; the patent of the latter claiming the sole 

 right of working an engine by steam in the cylinder, 2 

 drove the former to use two cylinders, in one of which 

 the expansion was carried out, as a means not described 

 in Watt's patent ; a lawsuit was the consequence. The 

 two engines when tried by Trevithick 3 performed an 

 equal duty of ten millions. In 1798 he tested the Dol- 

 coath atmospheric 63-inch single against Watt's great 

 63-inch double action. " The atmospheric performed ten 

 millions," precisely the duty of the patent Watt and the 

 patent Hornblower contests of six years before ; but the 

 Watt Dolcoath engine, then considered the best he had 



1 Memorandum in Trevithick's writing. 2 See vol. i., p. 40. 



8 See vol. i., p. 57. 



