The Sun.
London, England, 1817-07-22 00:00:00

STEANI BOATS.

Mr.-ALExANDERTILLoCR called in, and examined.
Will. you state where you reside ?—,At Isling-
ton.
And what is your profession ?-1 am Editor of
the Philosophical Magazine, aitd sometimes 1 ant
cailed on to act as 'an Engineer ; and I am Editor
and Proprietor of the Star Newspaper.
Will you be so good, as you know the object for
which we are Met, with regard to the safety of
persons in Steam Boats, to- mention what, sug-
geitions you-have- to make to the committee on
the subject ?—My opinion is, t hat
..attending
to what should be attended to in everyliteam en-
gine, and employing proper engineers, a steam.
engine would be perfectly safe, whether with high
pressitre or low pressure. The boilers ought al-
ways ,tia he furnished with safety valves ; and if
they suspect: the possibility of ,having a stupid man,..
one stf the valves should be covered and out of, hiat
'reach with a box oy,lr it,. but perforated so. that
you may see when the steam operates on it;
mercurial valve is also very good.; that is an in-
verted syphon, with a column of mercury pro-
portioned to the purposes for which it is to be em-
ployed. - .
1)o you apprehend much danger to arise, in
case of explosion, front that Mercury if it was.
employed ?—No, because the fubels always per-
pendicular, and it the mercury shoots out, it goes
away and falls down in rain s
.I am of opinion, a
boiler may be made safe either of wrought or cast
iron, but for great strain I would prefer cast iron,
Conn -- y to-the opinion of many people, und• the
reason I would prefer it is the same for which it is
preferred in making cannon. It is not possible
to get tbiekplatea of. wrought iron perfect through-
out, and you trust at last to rivets in joining them,
but cast iron boilers can be made of any strength
you please ; instead of • having a:boiler that will
stand sixty, it may be made to stand six hundred,
of either wrought or cast iron. Another reason
why 1 would prefer cast iron is, ' that the.sheet
iron 'corrodes much quicker and destroys by_oxy-
dation, so that, the -boiler may he safe when first
set up and stand its proof, but very soon become
unserviceable, or at least comparatively so. Boil-
ers should always be cylindrical, and for an ob-
vious reason, capacity should be got by length
and number rather than by diameter., There,is no
more danger to be apprehended from.stearn as to
bursting, than from the employment of Condensed'
air, only that the water may scald ; but as to the
danger of the fragments being scattered about, At
is the same with air as with steam, and yet all the
engineers constantly employ cast iron receivers,
condensers, or air vessels where pressure is
wanted.
Is not cast iron liable to suffer some material
injury from the contraction and expansion/0y heat
and subsequent cooling ?—Whether a' boiler be
made of wrought or of cast iron the metal expands
and contracts, and' expansion or contraction is -
more or less injurious in proportion as it is often
repeated, but it does not prejudice a boiler made of
cast more than one made of wrought iron. -
- Is it not more iiijurious to east than to wrought
iron boilers ?—No, I do not think it is.
In case of accident by explosion in a cast and
wrought iron boiler, which, in your opinion,
would be attended with the greatest mischief to
the persons about it ?-.--If an actual explosion takes
place, I should think front the cast iron, but I
conceive that a properly constructed cast iron
boiler would be stronger, and therefore would not
explode so soon. A boiler should be proved with
cold water, if it is to be applied to high pres-
sure.
Are you not aware that cast iron, notwithstand-
ing the greatest possible attention of the founder,
is liable to cavities in the interior substance of the
metal, which renders is uncertain when exposed
to great degrees of beat ?—There may be cavities
in cast iron, but a boiler being proved. to a strain
beyond that it is to be exposed to by heat, the
safety of the boiler is secured ; for the tempera-
tare never can be at that point which will endanger
a fractute. from that circumstance.
Do you mean by that answer to, say that the
rarefaction- of the air In that cavity may not he
so great by the-heat as to occasion its bursting ?
It never can, because the air that produced that
cavity was at a white heat at the time the iron
closed upon it, and it never can be brought to
such a heat in working a boiler ; ray opinion is,
that by a very high proof at the commencement,
and attention to it, you may always have a safe
boiler of cast iron.
[To be continued.] , •