94 Report of the Select Committee 
Have you ever seen an explosion of a cast-iron boiler }-«« 
No, I have not; | have seen the effects at Wells-street, I was 
upon the ruins immediately after ; the effect seemed to be tre~ 
mendous ; there it knocked down the whole building, which was 
a sugar-house of five or six stories high, and fragments appeared 
to be thrown in every direction; the boiler itself was shattered 
into a great number of pieces. 
If that had been a wrought-iron boiler and had burst, it would 
not have produced the same effect >—I think not. 
Are you at all aware, whether there is any preference of copper 
above iron, in the construction of boilers for high pressure steam- 
engines ?—I should think that copper is the best metal of all; 
the most ductile. —But I think at the same time, that with good 
wrought iron, boilers may be made perfectly safe up to the esti- 
mated strength of from four to five hundred pounds pressure per 
inch. 
Have you formed any opinion respecting the pressure per inch, 
necessary to drive a steam-boat through the water at the highest 
rate at which you have heard of any hitherto having gone ?—I 
have not turned my attention particularly to the use of high pres- 
sure steam, as applicable to steam-boats. But being the owner 
of a high pressure engine, I see no advantage at present in go- 
ing above forty or fifty pounds an inch in steam-engines. 
Supposing then that a boiler were constructed, with the in- 
tention of its resisting a pressure of steam equal to 300 pounds 
per inch, that it should be afterwards proved with a force equal 
to two hundred, and that it should be after that worked with a 
pressure under a hundred, do ycu conceive that any supposable 
danger could exist under such circumstances ?—None at all; 
provided the steain was limited to a hundred. 
It is understood of course, that the common precautions of 
safety-valves, the operation of which could not be impeded, 
should be applied to such boilers?—Yes; with respect to the 
valve of high pressure steam for working engines, I beg leave to say 
generally, that in Cornwall of late a most valuable improvement 
has taken place; and that if it is an object to save coal to steam- 
vessels upon a large scale, I do conceive tliat high pressure steam 
becomes an object of great importance to them. I mean if ap~ 
plied upon the principle that Mr. Woolf has in the first place 
introduced, but which has been applied by Mr. Sims, and I be- 
lieve by some others. 
You are of opinion these high pressure boilers might be made 
with equal safety as low pressure boilers ?—Quite so. 
Do you know any thing of the saving of coal produced by high 
pressure engines ?>—I have in my hand a statement of the work 
done by the engines on the principal mines in the county of Corn- 
wall, 
