54 Report of the Select Committee 
to that extent you mention, that danger would always operate? 
—It would not always operate, but it would be extremely liable 
to accidents. 
In fact, you yourself would not chuck to use a high pressure 
engine, from the difficulty which exists, either more or less ?— 
That is my opinion, 
Have you made any calculation what would be the force re- 
quired to be used to propel a boat in navigable rivers or canals ? 
—This does not admit of a definitive answer. It depends en- 
tirely upon opinion, how far one ferce would be dangerous and 
another nct ; but if steam-engines are employed for the purpose 
of propelling boats, that may be effected with perfect safety by 
the low pressure or condensing engines, where the pressure need 
not exceed six pounds to the inch. 
Of course that must depend upon the resistance to be made, 
and the velocity required for the boat?—Then | must make 
choice of a more or less powerful engine ; I think it just to state 
to the Committee, that there is'an advantage to be derived from 
the use of high pressure engines on board boats, which are ne- 
cessarily loaded differently at different times; this different load- 
ing requires a different power in the steam-engine, and the high 
pressure engine is capable of having this additional power given 
to it without any difficulty, whereas in the low pressure engines 
they are confined to the force first assigned to them. 
What is the maximum of the low pressure engines ?—I scarcely 
ever saw them beyond six pounds. 
In high pressure engines there is a great saving of fuel ?— 
There is in one, a peculiar kind of those called high pressure 
engines ; ; there is a considerable saving of, fuel in Woolf’s 
engines; but in the common ones, I believe there is but little 
saving. 
If therefore the engines were to be used where the saving of 
fuel would be of considerable consequence, high pressure engines 
of a certain construction would be better adapted for that pur- 
pose than low pressure engines ?—Where tlie saving was of much 
consequence, 
If engines were to be used at sea, it would be of considerable 
consequence, the engine and the fuel being contained in a smaller 
compass ?—Woolf’s engine is not in a much smaller compass. 
When you talk of the deterioration of the boiler, how long 
would a boiler, properly constructed and constantly used, be used 
with safety ?—That is extremely uncertain ; I have known one 
boiler worn out in six months, and another used for seven or 
fourteen years; the strength of cast-iron boilers is extremely 
uncertain; cast iron contracts in various degrees in different 
places, and therefore is liable to break, 
You 
