92 Report of the Select Committee 
eident happened. The second case that I heard of was in the 
North, a propelling engine (it was mentioned in all the papers); 
it was near Sunderland, of a boiler driving waggons ; the facts 
of the case I know to be these, from the engineer who made the 
boiler.—In the first place, they had a smaller boiler to the same 
engine; that boiler did not generate steam so fast as the engine 
could expand it, consequently there was never an excess of steam 
came out of the safety-valve, the engine-man therefore with im- 
punity screwed down his safety-valve ; it was never used. ‘The 
proprietor of the engine wishing to have more power, ordered a 
larger boiler, which had the power of generating nearly double 
the quantity, cof steam; this was sent, and a caution given by the 
gentleman not to attach it to the engine till he arrived; but 
that was not attended to ; the boiler was attached to the engine’ 
the man went to work as before, and he screwed down his safety- 
valve, not knowing, that though before he had a deficiency, he 
had now an overplus; he said he would make a good start of it; 
the boiler exploded, killed several people, and him among the 
rest; and the force was remarkable, as shown by the fragments 
of coal that were driven through the men’s clothes or into their 
bodies from the tram. The Wells-street was the third case; the 
safety-valve was loaded in this case. At Norwich I apprehend 
the safety-valve was loaded. ‘The only other case was in Treve- 
thick’s new high pressure boiler, the wrought-iron boiler; that, 
I should say, was something like a boiler formed of two ‘ares of 
circles; it burst without doing any hurt, and perhaps the cir- 
eumstance is not known to ten people besides myself. ‘The 
people were near it, and it did them no hurt. The reason it 
burst was, that a man very ignorantly took out bars which he 
should not and altered its construction. These are the only in- 
stances I know of the high pressure boilers. 
Do you consider low pressure boilers as safe from explosion 
under all circumstances ?—Only owing to the column of water 
that fills them; that is the only reason [ consider them as safe. 
If they are supplied by a column of water, then do you con- 
sider them as safe from explosion ?—I do not consider them as 
absolutely safe, because I know facts of their bursting; in case 
of their not being fed with a column of water they are very un- 
safe; for the construction of the boiler is weak in itself, and you 
have no dependence but upon a safety-valve, which may be loaded 
improperly, 
Do you conceive that a wrought-iron boiler may be rendered 
safe under all circumstances ?—I do consider that it may. 
State how ?—Principally by the use of a column of mercury in 
a syphon or tube, of sufficient size; when that mercury is dis- 
placed by the expansive force of the steam, which would be re~ 
gulated 
