The true northerner. [volume] (Paw Paw, Mich.) 1855-1920, 1872-03-29
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 l54 feet inches depth
of hold, 30 feet. AID about % beam.
The hull is constructed of live oak, red
ok, and yellow pine. She has screw
at both ends-at the after end, one
with three blades, twelve feet diameter
and fourteen feet pitch, Tor propelling
exclusively the forward end Is pro
vided with screw also, but something
a little different in its aspect. II has
six blades instead of three, and looks
like big whirligig. This screw, like
the one at the other end, is u.ade of
brass its diameter is the same, and it
weighs % 900 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 now 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.fye or eighty revolutions
per minute with thirty pounds of
steam The three-bladed propeller is
driven by Il single oscillatlng engine,
the same size and power with the
others. The steam is generated in five
tubular boilers, weighing twenty tons
each. These are situated amidships in
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 we'll 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 a
half cylinder, made of Z inch boiler |
iron, with heavy wrought iron rims and !
pinions. 1t is y 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 |
davlts overhanging the digging end Of |
of the boat, and is managed by means |
of a pair of powerful hosting 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 filled 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 davlts, is let 90 on the run. Its |
great weight carries it far into the mud. |
Then the big six-bladed screw is set in |
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 sutii-
cient 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 to 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.