64 Report of the Select Committee on Steam- Boats. 
proved, and so guarded against carelessness, there would be no 
danger whatever in any situation ?—Certainly not; neither in a 
steam-boat or an engiue employed in a manufactory or mines, 
or in any manner whatever. 
_ As-to the ceconomy in the use of coals, what is your opinion ? 
—My opinion is, that the high pressure engines in Cornwall 
have saved at least two-fifths of the whole consumption of coals 
in the county ; in some instances it has saved three-fifths. 
What means have you of ascertaining that fact?—In the pur- 
suance of my ordinary employment, I attend to the various en- 
gines in Cornwall, and compute their duty; the quantity of coals 
that is consumed by the engines is rendered to me on oath; it 
is the same that is sworn to at the Custom-house. The ascer- 
taining the weights which the engine lifts is carefully and cor- 
rectly measured; and from this I calculate the work performed 
by the engines, of which I make a monthly report, and find, that 
those engines which work with a high pressure steam are more 
ceconomical in their operations than those of the low pressure, 
so much so, that were the low pressure steam engines to be in- 
troduced into the mines of Cornwall, it would stop upwards of 
two-thirds of them. 
Is the paper which you have, one of those accounts ?—It is 
the account for the last month. 
[It was delivered in, and read ;— Extracts from these Reports 
are given regularly in the Phil. Mag.) 
And this account you declare, upon your own knowledge, to 
be accurate as to the particulars it contains ?-—I do. 
Do you consider it as important to the safety of an engine, 
that the boiler should be frequently cleansed ?—If a boiler is 
foul, if there is a quantity of mud in it, it may prevent the water 
from coming in contact with the iron, and in that case the boiler 
is liable to injury; [ have known a wrought-iron boiler to burst 
from that very cause; I never knew a cast-iron boiler to explode 
in any instance. 
Is there any difficulty in subjecting the boiler to the usual proof, 
every time it is cleansed ?—There is no difficulty whatever, any 
other than having the apparatus prepared for it, which is very 
easily done. 
Is that apparatus either expensive, or difficult of construction, 
or of application ?—No. 
Can it be applied with ease by any enginle-man or engine pro- 
prietor, who is at a!l acquainted with the construction or working 
of a steamn-engine ?—Yes; and the management of it is so plain 
that no person can misunderstand it, if they are unacquainted 
with all*the other parts of the engine. 
In what does this proof consist, and how is it performed — 
he 
a hd 
