on Steam- Boats. 175 
Do you know by whom it was published?—TI do not know; I 
have heard it was done by the proprietors of some of the steam- 
boats ; the letter I wrote was sent to the Morning Chronicle 5 
it was only within the last three days I saw it in that form. 
Have ycu been employed at all in constructing steam-engines 
for steam-boats ?—I have not. 
Were you acquainted at all with the accident at Norwich ?— 
No; but what I have heard. 
The object of this Committee being to insure the safety of the 
passengers on board steam-boats, will you favour them with your 
opinion as an engineer, what means are best adapted to insure 
that safety?—Ii should certainly recommend, that for steam- 
boats, the condensing engines should be used in preference to 
high pressure engines, seid I will give you my reasons why I do 
so. In the first place, the great advantage that has been pro- 
mised from a high pressure engine is, that it can be worked in @ 
situation where water cannot be procured, and therefore, under 
this circumstance it is for such a situation a valuable machine ; 
but in situations where water can be readily procured, it is not 
so. And in reference to the comparative price between a high 
pressure engine and a low pressure engine, and in reference to 
the space that it occupies, and in reference to the superintendence 
that it requires, I am decidedly convinced no ceconomy is pro- 
duced. Speaking to it asa matter of safety, it will be necessary 
for me to say, that experience has fully proved, that the maxi- 
mum of force to be obtained by a condensing engine, is when 
the steam is rarefied from three to six pounds on the inch; the 
engine is by far more efficient than when the steam is rarefied 
up beyond; and it will appear equally clear, that whether it he 
a cast-iron boiler or a wrought-iron boiler, or a copper boiler, 
the force of the engine is better performed by steam at three 
pounds and a half, than it is at any increased expansive force ; 
the boiler being subject only to three instead of six pounds, 1 at 
‘must be less liable to explode or burst at that than at an increased 
‘expansive force. I should further say, that every man that is 
called to work a condensing steam-engine, knows, that when his 
steam is at three pounds and a half, ib performs a greater quan- 
tity of labour than at any other time ; for if you increase it you 
throw a vast labour on the air- -pump and the condenser, # and retard 
the engine: therefore, a man has no inducement to increase the 
expansive force of the steam, he knowing that no useful end can 
be obtained by so doing, but giving himself additional labour 
and consuming more fuei, and performing less work. *I should 
also wish to state, that 1 yesterday made a sketch of what ap- 
peared to me to be a proper and efficient boiler for a steam- eo 
without 
