The herald., 1894-08-05
DOCTORING SHIPS.
PARASITES THAT SEND OCEAN YES.
SELLS TO THE HOSPITAL

ners of Construction-Ecmet About
! Drydocks and Their Uses.
The sea is q grand and yet treacher.
ous mother to the thousands of ships
that sail over its broad expanse, and aft.
er buffeting with its storms the ships
must go to their hospital for repairs.
This hospital is the drydook, and the
doctors are the army of careful work
men who look over carefully and repair
every faulty seam or broken rivet.
Salt water is teelning with parasites
of plant and animal life that cling to
the bottoms of ships, eat slowly yet
surely through wood and iron alike OF
rust it away, while they act as check
on the speed by vastly increasing the
resistance and friction of the water
against the ship The ''gods Of the
storms SEQ everywhere" and pick out
each weak seam or faulty rivet and
slowly and surely eat into the vitals OF
the ship, so that every few months il
sbecones necessary to examine and re-
pair the vessel. To do this she must
come out Of tho water. The drydook is
just a greatbox of wood, iron and stone,
connecting with the sea by a great gate
way. When tho ship is ready to enter,
the gate is shut and the water all pump
ed out; then the workmen, with prao-
ticed skill, place tho blocks at the bot
tom of the dock for the keel to rest
upon, taking the Dimensions from the
plans and drawings of the vessel. These
i'm place. the dock is flooded again the
gate opened and the ship hauled in.
The gate is now closed again, and while
the water is slowly pumped out and the
ship settles down the docksrs pull her
this way or that until she rests evenly
on the keel blocks. Then shores, OF
heavy wooden beams, are braeed from
the sides Of the dock to the sides of the
chip, and as the water is pumped away
the ship stands 'high and dry" yer.
stable "fish out of water, +" the bottom,
which was below tho water line, cover.
ed with seaweeds and parasites that
hide the defects they have caused.
Then the worlmen scrape and scoul
the unwelcome barnaoles and grass
away, the seams and rivets are all ex.
amined and repaired, fresh coat OF
paint goes on again, and as the dock is
again flooded the ship rises from her
hospital bed, and the wooden supports
are knocked away until she floats out to
sea again, healthy and strong" to
battle with tho wind and sea and the
enemies Of the flag she proudly flies.
When wood was used almost exclu-
sively in building ships, very easy and
convenient means was found to protect
tho under water portions Of the ship
from the insidious attacks of barnacles
and parasites Of plant and animal life.
This was done by covering the whole
bottom Of tho chip with plating OF
thin ouppsr, for the galvar,io action OF
the salt water UPON the copper was to
convert the ship and sea into vast bat
terry, whore the copper became the mega
tive pole and was slowly yet constantly
eaten away, the PARTICLES, as they fell,
taEngwith them the balnaoles and sea-
wesd as fast as they formed on the
ship, thus keeping the ships bottom
end sides always clean, sothat the speed
was NOT cut down by dragging the bar
nanles and yards of seaweed through the
wafer Yet even then the copper need
ed repairs; faulty timbers rotted and
crumbled away, SO that every few years
the ship had to go into drydook and be
thoroughly overhauled, each faulty tim
Der replaced and rusty bolt repaired IN.
til no loophoie was left for the sea to
work upon.
Bnt with the advent of iron in the
building Of ships the old means failed,
for where copper was placed over iron
the iron became the negative pole of the
great battery and was eaten away quick.
ly, riddling the bottom of the ship with
many leaks. Many devices were tried
the under water portions Of the vessels
were covered with a waterproof layer OF
wood which was then ooppered as be-
fore. but wherever there was any me-
tallio connection between the copper
and iron the whole force Of the battery
acted there, and holes were eaten in un-
expected ana inaccessible places, bring
ing in an element Of uncertainty and
enforcing great care in "sheathing' the
vessels, as the coating Of wood is called,
and the ships still had to go more often
than ever to the drydock.
Then the various methods of painting
the bottoms with protective paints have
been tried and ere used in all Of the
cruisers Of our navy. The skill of hun
dreds Of chemists has been exerted to
find paint that would act as the cop
per does and throw off the barnacles and
seaWeed Great prizes have been offer
ed, and fortune awaits the successful
discoverer Of such a coating for ships,
yet SO far none has been discovered that
acts completely, and the iron and steel
ships which start from port with fresh
ly painted sides and bottoms return in
few months coated with barnacles and
sea weed, which, as it trails in the wa
ter, very materially cuts down the speed
and power Of the ship. Then she must
be put in the dry dock and scrubbed and
sGaped and repafnted. Still worse than
the barnacles and the seaweed is the
water itself when it finds an entrance,
be it ever SO small, through the paint
to the steel below. Slowly but surely
it rusts out little pit, which extends
sometimes almost through the plate be-
fore the paint scale drops off and dis
closes the defect, which can even then
only be seen by putting the ship in dry
dock and examining every square foot