328 Report of the Select Committee 
Is it your opinion that a high pressure boiler may be con- 
structed so as to make it perfectly secure ?—That is a theoretical 
question to give an answer to; I should say yes, certainly; but 
experience proves that both wear out. 
What would be the construction, and what the precautions 
you should recommend, in order to ensure that safety ?—That it 
should be able to withstand the proof of two or three times the 
pressure to which you are likely to put it, or rather the pres- 
sure to which you should be limited ; if, for instance, you meant 
to work it at fifty pounds pressure, and it stand the proof of one 
hundred-and-fifty pounds, the presumption is, that it is se- 
cure; but in the course of two or three years all boilers wear 
out. 
What are the precautions that you would recommend to pre- 
vent a boiler being used at a greater power than what it was 
adapted for?—-By having an additional safety-valve, to which 
the person who works the engine should not have access. 
Is there any other precaution that you would recommend ?— 
I think that if it were made of malleable metal, such as iron and 
copper, it would be an additional security. 
What is the ground of your preference to malleable or wrought 
metal ?—It does not burst by an explosion, as brittle metal does, 
but tears ; it would probably rend at the joints. 
You do not mean then to say, that it would be impossible that 
a malleable boiler would burst, but that it is improbable that 
it would ?—It would burst, but it would not fly in pieces; the 
rent would create a natural safety-valve. 
Are you acquainted with the fact, that high pressure steam 
and water heated so as to raise that steam, do not scald in the 
same manner with water and steam at the heat of 212° ?—I am 
not acquainted with the fact; but I have no difficulty in believ- 
ing that the steam will not scald, although I should think that 
the water will. 
Do you think that if the safety-valves be properly adjusted to 
the strength of the boiler, and so constructed as to work. with 
perfect ease, and one of them put out of the reach of the engine- 
man, there is any occasion for the additional aid of a mercurial 
gauge ?—I should think not, 
Have you any particular suggestions to make respecting the 
construction of the boiler ?—The most convenient form of the 
boiler is, that it should be adapted to the shape of the boat; and 
I should think, that that being taken for granted, the safety 
would depend upon the strength of the metal, and not upon the 
form. It should be made of such strength, that any indenture 
would not affect it. Although the form approaching to cylin- 
drical is of course stronger than any other form, that which nearest 
approaches 
