332 Report of the Select Committee 
in ciameter than if composed of a number of tubes; and the 
risk of explosion is in proportion to its quantity of surface. 
Do you mean to say that, generally?—-With the same pres- 
sure, certainly. 
Would your boiler be as well adapted for a steam-boat, as 
those generally made?—Yes, they are calculated for every pur- 
pose ; they are generally adapted to high pressure steam; my 
patent was taken out for a safe boiler for a high pressure en- 
gine; indeed, in my own engines, I do not work the steam to 
that height as is done in what is called the high pressure engine, 
as the novelty of my engine is, that I work the steam twice over. 
What precautions do you take to prevent accidents ?—I al- 
ways make my boiler to stand from 14 to 20 times the pressure 
that [ ever make use of, 
What precaution do you make use of, to prevent a greater 
pressure ?—-The safety-valve is what we depend upon ; I always 
apply two safety-valves, as I have seen incidents where the valve 
has accidentally stuck fast and would not act; and I have a safety~. 
yalve, of a particular construction, that never can stick fast. 
Do you use mercurial gauges ?—Never for a safety-valve; } 
never found it necessary to have one, not for an escape, 
Have you any other precautions besides those you have men= 
tioned ?—Not any, but as to trying boilers to see that they are 
strong enough; that is the point that I recommended in my 
specification, that they should be proved by pressure every time 
the boiler is emptied for cleansing ; then to fill up the boiler 
with cold water quite full, and put an extra load of five or ten 
times the power of steam; and then, by a forcing-pump, to 
syringe water in till it lifts the valves; then there can be na 
danger, there can be no explosion. 
Suppose a cast-iron boiler, and a wrought-iron boiler of about 
the same form and capacity, to be exploded by the force of the 
internal steam, do you think that the mischief likely to be pro- 
duced by each of those, would be equal? taking any form you 
please, and exploding both, which would do the most mischief 3 
—I do not think the wrought-iron boiler would separate into so 
many pieces as the cast-iron boiler. 
Then do you think that the explosion of the wrought-iron 
boiler is attended with as much danger as the cast-iron boiler ? 
—In every thing, excepting what depends upon the fragments 
of the iron itself; I have no hesitation in saying, that cast-iron 
boilers are safer than wrought-iron boilers. 
Why ?—Because we can make them of a greater strength ; 
you cannot make a wrought-iron boiler so strung as a cast one. 
For high pressure you may have a boiler of cast iron ma 
than, 
