l 
latter ;* thus reversing the mode of application previously adopted 
in combined- cylinders by Woolf and his predecessor Hornblower. 
Notwithstanding an engine on this construction at Treskerby 
sometimes took the first place on the Report,+ scarcely half a dozen 
of the kind were erected.t Sims, however, was always averse to 
the use of very highly-elastic steam.§ 
About the same time Jeffree and Gribble—with the advantage 
of advice from Sims||—erected, at Dolcoath, the largest single- 
acting engine, until then, seen in Cornwall;§ which—like that 
set up some years before at Wheal Prosper**—was worked with 
steam of moderately high pressure in Trevithick’s cylindrical 
boilers ;tt and it immediately performed, and for several years 
continued to perform, exceedingly high duty.{t 
In 1820 a seventy-inch, and two ninety-inch single-acting en- 
gines were placed, by Woolf, on the Consolidated Mines ;S§§ all 
which were supplied with Trevithick’s boilers, but the fires within 
them were much shallower than those previously used in the neigh- 
bourhood; their performance, however, never equalled that of the . 
engine at Dolcoath. 
Waitt’s first patent|||| provided that all vessels containing dense 
steam should be enveloped with non-conductors of heat; a pre- 
caution which was, probably—to a greater or less degree—ob- 
served at the erection of every engine. For many years, how- 
ever, the coverings of the cylinders, steam-pipes, and boilers were 
as much neglected as the fittings of the stuffing-boxes and joints ; 
and—for want of the special arrangements which are now pretty 
general—the wet working-dresses of the miners were dried on the 
* Henwood, Hdin: Journal of Science, x., p. 37. Pole, Cornish Pump- 
ing Engine, p. 58. f 
+ Lean, Historical Statement, p. 48. 
+ Henwood, Hdin: Journal of Science, x., p. 37. Pole, Cornish pee 
ing Engine, p. 58. 
g Pole, Cornish Pumping Engine, p. 58. 
|| This statement is made on the authority of the late Mr. Sims himself. 
q Henwood, Edin: Journal of Science, x., p. 45. Taylor, Records 
of Mining, i., p. 156. Farey, Phil: Mag: and Annals, Viii., p. 312. Pole, 
Cornish Pumping Engine, p. 56. 
#* Ante, p. 47. 
+t Pole, Cornish Pumping Engine, p. 61. 
tt Henwood, Edin: Journal of Science, x., p. 45. Taylor, Records of 
Mining, i., pp. 156-158. Lean, Historical Statement, pp. 32, 42, 56. 
§§ Henwood, Hdin: Journal of Science, x., p. 37. Taylor, Records of 
Mining, i., p. 157. Farey, Phil: Mag: and Annals, viii., p. 312. Lean, 
Historical Statement, p. 353. Pole, Cornish Pumping Engine, p. 57. Smyth, 
Coal and Ooal-Mining, p. 187. Taylor, Farey, and Pole mention only the 
two last, Lean speaks of but one, of these engines. 
[||| In 1769. Fanny, Steam-Engine, p. 316. 
