170 Report of the Select Committee 
apply it in my own business, not as a moving power, but, for the 
purpose of communicating heat to different fluids, for which pur- 
pose I have required high pressure steam. I have a patent for 
a mode of applying high pressure steam to vessels of the largest 
capacity; and as in this ease all danger depends on the con- 
struction of the boiler, I should. wish to say a little on these boilers 
which | have found to be the most trust-worthy. I come quite 
unprejudiced as to any material, and as to any form; for if | could 
meet with a boiler which would answer the purpose I have in 
view better than that now used by me, I would adopt it; there- 
fore I shall give the Committee only such facts as have come 
within my own immediate knowledge. 1 have no wish to re- 
commend any particular construction, 
Will you be so good as to state from your knowledge, what 
species of boiler for a high pressure engine you would recom- 
mend in regard to safety ?—I consider the first and most mate- 
rial point to attend to in the construction of high pressure boilers 
is, that the diameter of such boilers should be small in propor- 
tion to their capacity; and that as small a proportion of the 
external surface of the boiler as possible should be exposed to 
the destructive action of the fire; and that the portion of the 
hoiler so exposed, should be so situated and guarded, that in case 
of explosion the least possible mischief would arise. In those 
boilers which I have made use of, no portion of the boiler is ex- 
posed to the action of the fire without its being constantly co- 
vered with water; and the fire is applied under an arch of not 
more than two feet and a half in diameter ; this provides against 
any extensive rent taking place in the event of explosion. ‘The 
boilers I have generally employed are constructed of malleable 
iron, commonly known by the name of charcoal iron, riveted 
together and secured by strong wrought-iron belts. From ob- 
serving the danger arising from the introduction of flat cast-iron 
ends, | bave terminated the ends of the boilers by wrought-iron 
ones nearly hemispherical; this mode of construction, as far as 
my experience goes, combines more strength and durability than 
any other. The precautions I have made use of to guard against 
the misuse of such boilers, have been by adapting to them two 
safety-valves ; one under the control of the engine-man, the 
other secured in a strong cast-iron case, locked down and loaded 
with such a weight as would suffer the steam to escape when it 
had arrived at an improper degree of expansive force. In order 
to add to the security given by safety-valves, I have likewise in’ 
every instance attached to the boiler a inuaicial column, the 
bore of which is proportioned to the size of the boiler; and I 
should consider an iron tube of an inch diameter sufficient ta 
guard 
