New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1873-05-01
An OPPORTUNITY FOR INVENTORS.

sHEATHING sHIPS-THE MEANS UsED-A NECESSITY
FOR MORE THOROUGH PROTECTION.
AS far back as 1898, in Sir Richard IIaw
knss Voyage to the South Sea-" 1nd page devoted
to the methods Of protecting ships from the
destructive effects OF the "teredo," ship worm"
In quaint Old English, he gives the methods employed
in different countries In Spain very thin sheets Of lead
attached, but this was not durabe double pankng
was tried but the perforated this shield with ease
canvass nailed used, but unsuccessfuly. good
plan, he says consists In charring the outside OF the
planks and then spreading pitch tar In China
some of varnish found TO work WELL but the
author frankly says he knows little about it, He also
mentions a compound of pitch and glass. In England
he says his father the inventor OF tho best
method. 1t consisted in two hcknesses OF extra plank
ing between which tar and hair in two layers; this
he says cheap and effective But pass from the old
methods to the time when copper could be made into
thin sheets at reasonable cost. Here was a metal
harder than lead, and apparently sufficient for ali pur
poses. At first much trouble was experienced with 1t
from the corrosive action OF the salt water the oxide
from its poisonous nature prevented the adherence
Of animals, but the copper rapidly destroyed.
Sir Humphry Dayy suggested the idea Of attaching on
the copper various places pieces of zinc ron which
at once made the copper sheathng electromagnetic and
capable therefore, Of resisting the action Of the
water but for certain this plan was dropped,
except for ships laid up in dock The present compost
ton Of sheathng metal is decided improvement over
the copper; IL Is cheaper,
but after much use be replaced it also suffers
from corroson great question presented for the in
yentve mind solve. is the discovery of efficient
for the protection Of iron vessels. Although the
hulls Of such ships not damaged by the ship
1t is found that great Of weeds and animals be-
through the water. Many compositions have been used
TO this fOung OF the bottom but none have been
ecua the application OF ytreOus plates has been tried
IN many cases but their ultimate success IL doubtful
In OF the best English ships the method OF sheath
ing with wood and copper, although very expensive,
ached TO the ship, then another thickness Is screwed
fast 10 this with copper screws care being taken to pre-
the copper and touching this the sheath
ing metal is attached In the ordinary manner Tns has
proved very ehectu hit Is not In general use chiefly
of its difficulty exists In iron
vessels from the corrosive action the iron propeller
when copper Is It's vicinity due 10 the electric
current established For tho ordinary Atlantic
frequent bookings and much paint are found 10
be "A sufficient protection Hot climates the worst,
rapid that IL Is absolutely necessary To protect the
plates in manner. IL IL accomplished as already de-
scrlbed, composition prOpellers being used. Tdll1w
mixed with substances has been plentfuly
spread on the Immersed pOruOn OF the snip whle III
dock This prevents anything sticking, and as long as
lasts protects the hull. At one time when the Great
Eastern cleaned, she found to have IN places
punches OF seaweed six feet in thickness rmy attached
This OF the result OF remaining unused FOR
space OF time. What remedy may be hlally discovered
IS impossible state, but IL will probably Inc sub
stance resembling enamel, capable OF being easily aud
cheaply applied To ship wnen IN dock. Ine necessity
for the discovery OF method much felt In ships
OF for during long cruise no docks being aceesi
BILE the bottom very dirty, and this the
speed OF the ship be reduced, while places the
plates become almost destroyed by rust.