hi 
naked or imperfectly protected vessels,* in and through which 
dense steam was generated, conveyed, and worked. At length the 
emulation excited by the Hngine-Reports compelled attention to 
the prejudicial influence of this exposure; and the use of non- 
conducting substances was resumed, with corresponding benefit ; 
yet without suspicion of the extent to which they could be advan- 
tageously applied. . In 1825, Grose|—one of Trevithick’s pupils— 
commenced at Wheal Hope} in Gwinear, the system of protection 
from which he,—and others subsequently—realized most im- 
portant results. The duty performed there, by an engine of sixty 
inches cylinder, having averaged— 
In 1825 ........ 40°8§ millions per bushel; 59-2 millions per cwt. 
6p USB SGanoace 45-4 is ; 54:6 50 59 
of USB Co edoaus 47:3 Hn an 56-4 e A 
AES 2.83 ie, oyeietaisiice OPS) 55 i 84: ‘5 
The improvements thus begun were yet more preeueilly omied 
out, by the same engineer, on an engine of eighty inches cylinder 
erected at Wheal Towan4 in the latter part of 1826. At first, 
when protected, in the ordinary manner, with two, three, or four 
inches of ashes and saw-dust,—it realized nearly 50 millions* * per 
bushel (59-5 per ewt) ; afterwards, however, the protection was 
increased from four to ten, and again from ten to twenty inches 
in thickness, and at each increase the duty proportionally im- 
proved.tf An engine of ninety inches cylinder, which had been 
* Head, Quarterly Review, xxxvi., p. 89. Report of Commissioners 
appointed to inquire into the condition of Mines in Great Britain, p. xxii; 
Epitome of Evidence, pp. 91-94. 
+ Samuel Grose was born (of Cornish parents) at Nether Stowey, in Somer- 
setshire, 15th of March, 1791, and died at Wall, in Gwinear, 12th June, 1866. 
{ Taylor, Records of Mining, i., p. 158; Annales des Mines, 3me Série, ii., 
p. 63. Farey, Phil: Mag: and Annals, vili., p. 318. Henwood, Jbid, x., p. 
100. Lean, Historical Statement, p. 57. Pole, Cornish Pumping Eng gine, Pp. 63. 
§ Henwood, Edin: Journal of Science, x., p. 48. 
|| Lean, Historical Statement, p. 78. 
q ‘‘ A remarkable improvement in the duty of steam-engines has of late 
“taken place in two instances on mines in Cornwall.... The first engine in 
“which this improvement appeared was one erected at Wheal Hope, of 
‘¢ 60-inch cylinder, working single as usual.... [An] engine afterwards built 
“by Captain Grose.... [has exceeded] by nearly 50 per cent. what had 
‘hitherto been attained.... This great improvement is in progress of being 
‘‘applied to other large engines in the same district.” Phil: Mag: and 
Annals, ii., p. 309. 
The Engineer (6th May, 1870), xxx., p. 277. 
** Observations on the performance of a Steam-Engine at Wheal Towan, 
by W. J. Henwood, Truro, Brokenshir, 1828. Edin: Journal of Science, ix., 
p. 159. Herschel, Natural Philosophy, (Cabinet Cyclopedia), p. 59. Taylor, 
Records of Mining, i., p. 158; Annales des Mines, 3me Série, ii., p. 63. 
Lean, Historical Statement, p.57. Pole, Cornish Pumping Engine, p. 63. 
++ Henwood, Hdin: Journal of Science, x., p. 57. 
D2 
