on Steam-Boats. 89 
which it was to be subjected in the ordinary way of business, 
and that proper safety-valves were applied, it would be safe’as 
long as the action of those safety-valves were insured, and so 
long as the perfeetion of the metal could be upheld. 
lf a boiler was found to sustain the pressure of 100 pounds to 
a square inch, and such boiler had been tried, and it was found, 
before used, that. it would-bear.a pressure of 200 pounds upon 
the inch, would not such a boiler be perfectly safe to be used, if 
the safety-valve was so constructed as to open itself at the pres- 
sure of sixty?—I cannot pronounce it perfectly safe, and I must 
give this reason ;—I think if a boiler was prepared to sustain 
100 pounds, and strained to 200, it might afterwards perhaps 
burst at forty, the straining having injured it. 
In the situation of steam-boats, might not the unskilfulness 
of the sort of persons who manage them render any steam-boat 
unsafe ?—I] do not know how that could be the case; they might 
by wilful perversion of the proper principle of management ren- 
der them unsafe to a comparative extent; for instance, if there 
was half the pressure there would be but half the danger under 
like circumstances. 
Do you or not apprehend, that a boiler upon a proper con- 
struction, of wrou ght metal, may be tried with a certain force, 
so small in comparison with that pressure which it is intended to 
bear, as not to incur any risk of being injured in the proof, and 
have a complete surplus of strength, so as to enable it to be af- 
terwards used without any danger in the use ?—I should pro- 
nounce such a boiler to be perfectly safe, and so long as it main- 
tained those properties it would continue so. 
Have you considered how safety valves may be constructed as 
adapted to boilers, so as to put it out of the power of the person 
having the management of them improperly to load them, or to 
alter their nature ?—The most simp!e mode which has suggested 
itself to me is, to have a double safety-valve, and to lock one up 
and to have it examined once a week, or as often as may be ne- 
cessary, to see that its action is perfect. 
If there were those two safety-valves, one under the manage- 
ment of the person who had the direction of the boat, and the 
other safety-valve under such guard that he could not prevent 
its action; such a boiler would, in your opinion, be safe?—That 
would be more safe than any I ave ever seen, 
Have you ever witnessed the different effects of the explosion 
in cast and wrought iron boilers ?—-No; I have seen wrought 
iron vessels that have been burst—torn out, as it were. 
Did you never see a cast-iron vessel burst ?>—Yes, many; the 
wrought i iron generally tears and opens out, to admit of the fluid 
escaping ; it is generally the fluid which does the mischief min 
the 
