The native American., 1838-07-21
THE GREAT WESTERN.

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interesting detailed description of the machinery
Of the Great Western, by one of the gentlemen
who went out and returned in her. AS the resi-
dence of Lieut.. w. F. Lynch, of the U. S. Navy,
is in the neighborhood Of Frederick, we presume
that we safe in assuming that he is the author
Of the excellent and perspicuous article which we
subjoin.
"The Great Western steam ship is worked by
La pair of low pressure engines, constructed SINH
lary to most engines used in British steam navi-
cation. The great distinguishing feature of such
engines is, that the whole of the machinery is
under deck, although the cylinders are worked
vertically.
The beam of the engine is not placed above
the cylinder as in our boats, but pair of beams
are placed below the cylinder, and answer the
same purpose, at the same time that they bring
la great portion of the machinery below the water
line, and do not hamper the deck. The stroke
of such engines is shortened, though not necessa-
rily, by this arrangement, and in the G. w. it is
only seven feet.
The two engines are connected to the main
shaft on which the paddles are fixed, and in case
of an accident to one engine the other continues
to work both paddles or wheels, by dsconnect-
ing the connecting rod of the deranged engine.
This was the case in the outward voyage, when
one engine propelled the G. w., during 81 hours,
at the rate of 81 knots per hour.
These engines are each 200 horse power !:
they are worked by steam, not exceeding 81 lbs.
per square inch. An apparatus for reducing the
steam by expansion is attached, but rarely used
There are four boilers, each lOa feet long, 81
feet wide and l6 high. There three fire.
places to each floor, which terminate in fiue
that runs through the boiler, an extent of about
|26 feet, before it passes into the smoke funnel.
These four boilers are connected by valves to
one general steam pipe which supplies the two
|engines. Any one boiler can be shut off at plea
sure, and as three boilers with little extra fuel
can raise sufficient steam, the fourth can be cleans
ed out whenever required. The four boilers are
more than sufficient for the work, and consume
very little more coal than three; and at the same
time the iremen are not hurried, and the doors Of
the furnaces are repeatedly thrown open to keep
down the steam.
The consumption Of coal, both on the outward
and homeward passage to the United States, did
not exceed 81 lbs. per horse power, per hour.
In the toughest part of the homeward trip, when
the ship was week out Of port, and in better
trim from having consumed a considerable guam
titr of coal, the consumption was 5 to per hour.
The inconvenience to which steam boilers have
been heretofore subjected by the deposition of
salt and earthly matters, was obviated on board
of this ship, by peculiar arrangement, the in
vention of Messrs. Mandsley, Sons s. Field.
In Marine steam boilers, il is usual to blow off
La portion of the dcnsest salt water from the bot
tom Of the boiler, by means of a pipe or blow off
cock. In this manner, portion of the strongest
brine is forced out--but the quantity is limited
and much fuel wasted by the loss OF heat.
IN octb tbo ~ Mo, br,, II,
pump is attached to the bottom of each boiler,
and draws off constant stream of brine, the loss
Of which is supplied by pipe conveying hot wa
ter from the reservoir, which, pouring into the
boiler, keeps up a constant current, thereby pre-
venting decomposition and subsequent concretion.
Supposing the density of the water Of the ocean
to be 100, and that deposition cannot take place,
| in other words that the waters would hold the
salt and other earthly matters in solution, until
its density is reduced to &c Odds, the density of
the water in the boilers of the Great Western
was rarely less than 90. At the expiration of
| each trip, the boilers were as clean as if fresh
water only had been used. To ascertain the pro-
per quantity to be drawn off, and to regulate the
pumps accordingly, the density of the brine is
ascerained by letting portion OF it cool and try
ing it with an hydrometer. This simple substi-
tute for the old plan of blowing off has proved
so effcient, llat IL VIII no dOuDt De generally
adopted.
The boilers of the G.. w. are ofwrought iron,
square, with wagon tops. The maximum pres
sure is 81 lbs. to the square inch The moment
that the pressure of steam exceeds that amount,
the safety valve raises and the surplus steam
passes through the safety-pipe, TO the upper air.
From their shape and size, these boilers could
not withstand pressure of lbs. to the square
inch-and if they TO burst with that pressure,
only those in the engine and fire rooms would
suffer-the passengers and ship would escape
uninjured. But to guard against such an acci-
dent, which, on the ocean would produce great
eventual inconvenience, and in our own boats, for
the protection of life itself, it would be advisea
BILE to have two safety valves to each boiler, one
of each loaded to the maximum pressure it woult
be perfectly prudent to carry, and then cased ant
locked up, only to be visited by the commander
The others, as at present, accessible to the engi
neer. By this means, the engineer can alway.
diminish, but never increase the pressure, and by
consequence the danger. Rash and inexperienced
as many of our steamboat captains are, it would
often be unsafe to entrust the keys of the safety
valve cases with them. Unless they have been
proved perfectly competent and trustworthy
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