The Durham daily globe. (Durham, N.C.) 1889-1894, 1894-07-16
DOCTORING SHIPS.
PARASITES THAT SEND OCEAN YES.
SFLS TO THE HOSPITAL.

utT oI tOnSlG AbOuf
Drydocks and Ihsft Uses.
The sea is a grand and yet a Preacher
Gus mother to the thousands Of shiDs
that sail over its broad expanse, and aft
CT buffeting with its storms the shiDs
must go to their hospital for repairs.
This hospital is the drydock, and the
doctors are the army Of careful work
men who look yer carefully and repair
every faulty seam OF broken rivet.
Salt water is teeming with parasites
Of plant and animal life that cling to
the bottoms Of ships, eat slowly yet
surely through wood and iron alike or
rust 1t away, while they act as a check
on the speed by vastly increasing the
resistance and friction Of the water
against the ship. The gods Of the
storms see 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 it
becomes necessary to examine and re-
pair the vessel. To do this she must
come out of the water. The drvdOck is
just a great box of wood, iron and stone,
connecting with the sea by a great gate
way. When the ship is ready to enter,
the gate is shut and the water all pump
ed out; then the WOrkmcn, with prac-
ticcd skill, place the 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
in place, the dock is flooded again, the
gate opened, and the ship hauled III.
The gate is now closed again, and while
the water is slowly pumped out and the
ship settles down the lockers pull her
this way or that until she rests evenly
on the keel blocks. Then shores, or
heavy wooden beams, are braced from
the sides Of the dock to the sides of the
ship, and as the water is pumped away
the ship stands thigh and dry, " a yer
liable fish Out Of water, " the bottom,
which was below the water line, cover,
ed with seawceds and parasites that
hide the defects they have caused.
Then the WOrkmen scrapc and scOur
the unwclCOme barnacles and grass
away, the seams and rivets are all cx-
amined and repaired, a 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, "hcalthy and strong" to
battle with the wind and sea and the
enemies Of the flag she proudly flies.
When wood was used almost exclu-
sively in building ships, a very easy and
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the under water portions Of the ship
from the insidiOu5 attacks of barnacles
and parasites Of plant and animal life.
This was done by covering the whole
bottom Of the ship with a plating Of
thin copper, for the galvanic action Of
the salt water upon the copper was to
convert the ship and sea into a vast bat
terry, where the copper became the mega
tive pole and was slowly yet constantly
eaten away the PARTICLES, as they fell,
taking with them the barnacles and sea-
weed as fast as they formed on the
ship, thus keeping the ships bottom
and sides always clean, so that the speed
was not cut down by dragging the bar
nacleS and yards Of seaweed through the
water. Yet even then the copper need
ed repairs; faulty timbers rOtted ar1
crumbled away, so that every few years
the ship had to go into drydOck and be
thoroughly O~verhauled, each faulty tim
Der replaced and rusty bolt repaired un
til no loophole was left for the sea to
work upon.
But with the advent of iron III 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
We're covered with a waterproof layer Of
wood, which was then cOppCrcd as be-
fore, but wherever there was any me
tallic connection between the copper
and iron the whole force of the battery
acted there, and holes were eaten III UNI
expected and inaccessible places, bring
ing in an element of uncertainty and
enforcing great care in 'shcathing' the
vessels, as the coating of wood is called,
and the ships still had to 90 more often
than ever to the drydOck.
Then the various methods Of painting
the bottoms with protective paints have
been tried and are used III all of the
cruisers of our navy. The skill of hun
dreds Of chemists has been exerted to
find a paint that would act as the cop
per does and throw off the barnacleS and
seaweed. Great prizes have been offer
ed, and a fortune awaits the successful
d~iscoverer of such a coating for ships,
vet so far none has been discovered that
acts completely, and the iron and steel
ships which start from port with fresh
" painted sides and bottoms return IN a
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 ana
scraped and repainted. Still worse than
the barnacles and the seaweed Is the
water itself when it finds an entrance,
he II eyer so small. through the paint