188 THE WATT AND THE TREVITHICK ENGINES. 



lished about that time, in one of which, after a personal 

 examination of the engine, Mr. W. J. Hen wood 1 and 

 others reported a duty of 92*6 millions with a 91-lb. 

 bushel of coal. 8 



Mr. Rennie had been a pupil, a fellow- worker with 

 low-pressure Watt, and while his son, Sir John Bennie, 

 was examining the high-pressure steam expansive 

 engine erected by Trevithick's pupil, Captain Samuel 

 Grose, under the management of Trevithick's friend, 

 Captain Nicholas Vivian, the latter was engaged in 

 reporting on certain low-pressure steam-engines in 

 Wales, one of which was a Newcomen's atmospheric, 

 probably the last of its race, whose principle of con- 

 struction was a century old, working in company with 

 the Watt low-pressure steam vacuum engine, then half 

 a century old, the principles of both systems being on 

 their last legs, and under the care of Trevithick's 

 supporters. 



During this jumble of engines, old and new, without 

 a clear comprehension of their differences in principle, 

 Trevithick, who had just returned from America, and 

 lived within a few miles of Wheal Towari, looked on 

 unconsulted and unconcerned on questions which in his 

 mind had been settled by him in Dolcoath fifteen or 

 twenty years before. The writer, during the Wheal 

 Towan controversy, was the daily companion of Trevi- 

 thick, and made drawings of the engine at the works 

 of Harvey and Co., of Hayle, where it was constructed 

 about 1827. 



Captain Samuel Grose's Wheal Towan engine was 

 in general character similar to his teacher's Dolcoath 



1 Address, Royal Institution of Cornwall, by W. J. Henwood, 1871. 



2 Trevithick calculated 84 Ibs. to a bushel ; Watt generally 112 Ibs. ; Lean 

 94 Ibs., but latterly 112 Ibs. 



