xlvi 
drical tubular boiler ;* a kind of boiler which—having superseded 
boilers of all other kinds—long has been, and still is, exclusively 
used in Cornwall. Of this improvement it is scarcely possible to 
exaggerate the importance.T 
In 1801-2 Trevithick constructed, for driving a saw-millt at 
Marazion, a high-pressure engine of small size which was worked 
by steam of at least thirty pounds on the inch above atmospheric 
pressure.§ In 1806 he erected a larger engine, of the same 
kind, “for drawing” “ores at Dolcoath,”|| and worked it with 
steam of “nearly forty pounds to the inch." In 1815 he supplied 
Herland with a pumping-engine of thirty three inches pole** on 
the like principle, and worked it with steam of one hundred and 
thirty pounds on the inch.t+ High-pressure (non-condensing )— 
engines, however, found no favour in this County; and many 
years have elapsed since the last of them ceased to work. 
* Taylor, Phil: Mag: and Annals, i., pp. 127-128, Fig. 1. Henwood, 
Edin: Journal of Science, ix., p. 159, Pl. ii., Mig. 12. Farey, Phil: Mag: 
and Annals, vili., p. 313, Note. Combes, Annales des Mines, 3me. Série, 
v., pp. 367-369; L’ Exploitation des Mines, iii., p. 683, Pl. lxi., Fig. 3. 
Pole, Cornish Pumping Engine, p. 60. The Engineer, xxxi., (5th May, 1871) | 
. 297. 
F + ‘It has been found.... that the fuel goes further in [these boilers] 
than in any others yet tried.” 
Taytor, Phil: Mag: and Annals, i., p. 128. 
“To Captain Trevithick is due the form [of boiler] which is now 
‘generally adopted, and from which doubtless considerable advantage has 
“arisen.” Tayuor, Records of Mining, 1., p. 155. 
‘Better boilers.... for high pressure steam.... were first brought into 
“use by Mr. Trevithick in 1804.” Farry, Phil: Mag: and Annals, viii., 
. 3138. 
Se It is impossible to over-estimate the benefit conferred by the late Mr. 
«‘Trevithick on the mines of this county. The cylindrical boiler effected a 
“saving of at least one-third in the quantity of coal previously required. I 
“remember that in 1812 our house at Scorrier paid [him] £300, as an ac- 
“ knowledgement of the benefits received by us in our mines from this source 
‘ alone.” 
~  Wiit1ams (Micnart); Epmonps, Lond’s-End District, p. 255. 
Phillips and Darlington, Records of Mining and Metallurgy, p. 87. 
+ This machine, in which circular saws only were worked, was—within 
my recollection—removed to Perran Wharf. 
§ Henwood, Phil: Mag: and Annals, x., p. 97. 
|| Pole, Cornish Pumping Engine, p. 45. 
q Myr. Trevithick’s letter, of 18th February, 1806, to Mr. Davies Gilbert. 
Pole, Cornish Pumping Engine, p. 162. 
«* “‘Tnstead of a piston working in the main cylinder of the steam- 
“engine, I use a plunger-pole, similar to those employed in pumps for lifting 
“ water, and I make the said plunger-pole nearly of the same diameter as 
‘“‘the working-cylinder.” Truvirnick, Patent 6th June, 1815. Pouz, Cor- 
nish Pumping Engine, p. 57. 
++ Mr. Francis Trevithick, MS. (Extracted from his father’s papers.) 
