60 Report of the Select Committee 
of the vessel assume a diagonal or an oblique position,’ the alti- 
tude of the column would be lessened, and its consequent pres- 
sure upon the steam lessened. 
Are you of opinion that there would be much difieulty in 
guarding against such an inconvenience as that?—Yes, { think 
there would, generally speaking; but a well constructed salety~ 
valve would answer all the purposes. 
Are not the safety-valves applied to the low pressure engines, 
even when the column of water is used to supply the boiler?— 
Most frequently they are; I have seen some without. 
Did you never hear of the pressure in a condensing engine 
being raised by mismanagement as high as 19 or 20 pounds 
per inch ?—No; I do not recollect that 1 ever met with such a 
circumstance ; I have no doubt that it has taken place. 
If such a circumstance may take place with a low pressure 
engine, do not you think that, according to the general catcula- 
tion of the strength of their boilers to resist the usual pressure 
to which they are subjected, more danger would arise than in 
almost any case which could happen to a high pressure engine 
with a boiier properly adapted?—No, decidedly not ; according 
to the general construction of low pressure boilers, they are so 
riveted together to withstand the low pressure they are intended 
to bear, and they always give indications of an increase of pres- 
sure long before | should apprehend any danger from it; I mean 
by the joints giving way, and the steam forcing a passage ‘through 
them. 
Do you mean to apply that to the cast-iron boilers ?—No, 
certainly not; to the wrought-iron or copper boilers. 
The question before put was meant to apply to a low pres- 
sure engine, fitted up with a cast-iron boiler? — As applied 
to the cast-iron boiler, | should say, that being constructed to 
bear a less degree of expansive force, an explosion would sooner 
take place, and therefore would be less dangerous. 
Less dangerous in comparison with what ?—With a high pres- 
sure boiler. 
Do you mean to say, that an explosion of the cast-iron boiler 
of a low pressure engine which should be burst by an improper 
degree of pressure, would be less dangerous than the rending of 
a wrought-iron boiler, occasioned by a much higher degree of 
pressure?—I gave my answer as connected with the former 
question, with regard to the liability to danger from low pressure 
boilers; I take for granted, that if a boiler is constructed to be 
applied to a low pressure engine, that a commensurate strength 
will be applied to the materials of the boiler, and that in the 
case of applying a boiler to a high pressure engine, an adequate 
strength must be used there to the pressure intended ; therefore, 
if 
