334 Report of the Select Committee 
But those valves are capable of being loaded up to the full ex- 
tent to which the engine has been proved ?—Yes. AA 3 
Is it not easy and common so to construct one of the safety- 
valves, of which you have spoken, as that the engine-man shall. 
not be able to load it beyond the pressure intended ?—One may 
be locked up, and very easily kept from the engine-man. 
When that one is so locked up and kept from the engine-man, 
is it possible, according to the common calculation of events, 
that the boiler should then explode if the valve works freely ?— 
I do not conceive it possible that it could. 
Is it not easy so to construct the valve as that its operation 
shall not be hindered by any accident, such as adhering to the 
sides or clogging from fouling, or any thing of that sort ?— Very 
easily constructed, so as not to be liable to those accidents. 
Do you then see any reason why, in any situation whatever, 
the use of an engine should be limited to the low pressure, or 
that which is usually called the condensing engine?—By no 
means in the world. ; 
Do you conceive that there is any difference in the liability to 
explode, between the boilers constructed of wrought and of cast 
iron ?—I should conceive that cast iron could be made much 
stronger than wrought iron, with less difficulty; [ conceive it to 
be a very difficult thing to make a wrought-iron boiler so strong 
as we can have it cast: we have some of our boilers made two 
inches thick ; and to make a wrought-iron boiler equally strong 
as that, would be very difficult to be accomplished by workmen. 
Supposing a east iron and a wrought iron to be of the same 
form, and each of them to. be exploded by too great an internal 
force being applied, which of the two do you think is likely to 
produce the greatest mischief in the explosion ?>—Certainly, a 
cast-iron boiler is likely to separate into more parts than a 
wrought may be, and is likely to do more mischief. : 
What accidents have happened to steam-boilers within your 
own knowledge, working either with low or high pressure steam? 
—I have known of no accident with high pressure steam and 
cast-iron boilers; but I have known an accident happen work- 
ing with Boulton and Watt’s low pressure engine, which was on 
the 28th of November!811,in Wheal Abraham mine; a wfought- 
iron boiler working with low pressure steam exploded there and 
scalded six men, three of whom died in the course of a week 
afterwards, 
Were any persons at that time killed by the fragments of the 
iron ?—No 3; it was entirely by the steam and the water. 
Do you recollect any instance in which a wrought-iron boiler 
exploded, so as that any persons were killed by the fragments ? 
—I do not, 
Do 
