Marshall County Republican. (Plymouth, Ind.) 1856-1878, 1872-03-28
A Marine Curiosity.


A dredge-boat recently built at
Greenpoint. L. l., and now being fitted
with machinery at New York, destined
for work at the mouth of the Mississip-
pi, is thus described
Her length is 154 feet inches: depth
of hold, 80 feet, and about % beam.
The hull is constructed of live oak. red
oak, and yellow pine. She has a screw
at both ends-at the after end, one
with three blades, twelve feet diameter
and fourteen feet pitch, for propelling
exclusively the forward end is pro-
vided with screw also, but something
little different in its aspect. 1t has
six blades instead of three, and looks
like a big whirligig. This screw, like
the one at the other end, is made of
brass; its diameter is the same, and it
weighs $4,000 pounds. The blades are
made separate, and the boat carries ex-
ira blades, so that, in the event that
any one should break, it can be taken
out and new one substituted. The
forward screw performs two offices,
viz: that of impelling the vessel
through the water by a drawing on pro-
cess, and digging in the mud and sand.
1t is worked by two oscillatings, forty
inch bore by four feet stroke, and will
perform sixty-fve or eighty revolutions
per minute with thirty pounds of
steam. The three-bladed propeller is
driven by single oscillatng engine,
the same size and power with the
others. The steam is generated in FIVE
tubular boilers, weighing twenty tons
g. i i. /
the bottom of the hold the engines to
work the propeller are abaft the boil
ers, and those to work the forward
screw are forward of them. The shafts,
as well as the other parts of the ma
chinery, are ponderous, corresponding
with the nature of the work the boat is
to be employed at. Besides the six
bladed screw for digging there is also a
large scoop or drag, in the shape of
half cylinder, made of inch boiler
iron, with heavy wrought iron rims and
pinions. 1t is II feet deep, 90 feet con
cave linear measure, and will drag away
fifteen tons Of mud or sand at load.
This scoop is suspended from two strong
davits overhanging the digging end Of
OF the boat, and Is managed by means
of a pair of powerful hoisting engines
forward. Situated Immediately under
the boilers are the sinking tanks. of
which there are eight, each one capable
of holding eighty tons of water The
actual draft of the boat is fifteen feet.
but with the tanks filed it is increased
to twenty-three feet, SO that she can
remove /. stratum of mud eight feet
thick.
The mode of working is this: The
boat is first driven, light, as far up on
the bar or bank as possible. Then the
scoop or drag, which hangs suspended
from the davits, is let 60 on the run. It's
great weight carries it far into the mud.
Then the big six-bladed screw is set in
motion, and at the same time the pro-
peller at the other end commences
whirling, to pull the boat off The six
bladed propeller loosens up the mud,
and adds greatly to the impelling
power, which, when both are working,
is tremendous, dragging the great
scoop, with its freight of fifteen tons of
mud, out to sea.
The dredge-boat is registered at 900
tons capacity, yet she has power suffi-
Gent for vessel of 1000 tons, or four
vessels of her own size. AS the mud is
worked away, the sinking tanks are
gradually filled, the boat settles deeper
in the water and the digging apparatus
works in deeper mud.
The boat is built in the most stanch
and is perfectly seaworthy. She
is brig-rigged. Her bottom is of solid
oak, eighteen inches thick, and will
stand any strain 10 which it is liable to
be subjected. When at sea she will
work both propellers, one pulling and
one pushing, and it is supposed that
her speed will be eighteen miles per
hour.