The New York herald., 1879-02-05

sequent uron strain would occur within the very
small proportion OF the length occupied by the rivet
OF postage stamps with both hands II would break
on line marked by the holes and nowhere else.
OPPOSITE KxrREsrEs OF TEMPERATURE.
Imagine structure in the form OF iron ship
sailing through the Gulf Stream where the tenpera
tnre is at times as high as eighty degrees suppose
also, that her propulsion requires the burning OF
forty or fifty tons OF coal every twelve hours. II is
easy to conceive that the temperature of the entire
above eighty degrees. and especially in the upper
part. The deck beams and the inner and outer
skin of the ship would, in consequence, be in
creased in length until the upper part would exceed
that of the keel II there should be any ahwart ship
fore and aft bulkheads, these having the hot afr
on each side of them would be also expanded almost
much as the deck beams above Thus there would
be q tendency to widen as well as to lengthen tho
upper part OF the hull, while the bottom would be
restrained from expanding. in the Gulf Stream,
by the lower temperature of the water Thus there
would DO very severe strain exertcd which would
tend to separate the bottom from the keel.
THE FoRcE OF EXPANSION.
Now. suppose that the ship emerses from the
Gulf Stream and comes into the neighborhood Of an
iceberg. For great distance, and in al directions
round about the latter the water is reduced in tenn
upon the ship is that her bottom is yet more
tractcd. and that with suddenness,. too. The differ
their adjustment is destroyed. they pull apart
and she goes to the bottom. taking everybody
with her. and her fate remains forever mystery.
bar of iron inch in thickness and foot long
is increased l5 900 part OF its length by an increase
of temperature of eight degrees An equal extension
in length occurs when weight of 2 900 pounds is
pended by 1t. Consequently it expands with the
force of 1000 pounds for every increase OF teper;-
ture of eight degrees With increase of tenpera-
ture of eighty degrees the force would DO equal to
about sixteen thousand pounds With this proportion
of temperature to force in view it is easy to conceive
what must be the enormous strain upon ship
W hen the bottom Is 30 much colder than the top. In
building ronShips far less than this rate OF tension
is allowed as margin of safety. The regular test is
to make ship strong enough to support its own
weight il suspended 10y the stem and the stern. but
this standard is without reference to the unequal
expansion"
this dangerous weakness In iron?"
'I would recommend the building Of composite
ships. The frame should be of iron set upon a
wooden keel. Tho frame should be made III sections:
each section not more than ten fifteen feet III
length. The outer and inner SKINS all the fore and
art strakes the keelson, the waterway, the waes the
decks and the planking should all bo of wood
I'm ship so constructed would not the pulsaton
OF the wood and the iron conflict to such adegree us
to prove injuriousY
where 1t il of wood there is no such danger Bulk
heads could be applied to advantage and there could
required. They could be either of iron or OF wood.
as the lateral expansion would not be injurious"
Gould you suggest any plan by which the amid
ship compartment could be made smaller?
II do not know how the engines could be made to
occupy less space 1t would doubtless be advan
tage II they were separated from the boilers by Wa
tertight bulkhead."
Wooden ships are far the safer" said Mr.. Wizard
have sailed constantly for one hundred and ten and
one hundred and fifteen years, and yet, when they
at last laid up in the dockyard they just
sound in their timbers as the day when they We're
built"
| A STEAMERS sEAwoRTHINEss TESTED BY HER
REpUTATIoN--A RECORD OF MIsHAPs PRO
POSED.
New York, Feb. A. 1879.
To THE EDITOR OF THE HERALD:-
A man must be blind indeed not to see in the
HERALD the embodiment Of every quality that is q
constituent of push enterprise and devotion to the
welfare of the American people. Your articles on
Safety at Sea- "Bulkhead System" &C., pecu-
lary important. illustrating they do careless
that pervades the whole merchant marine in
gard the absence of regulations for closing bulk
head doors. and which demands the immediate en-
forcement of new rules 10 provide against this grave
danger. would like to suggest. in connection
with this subject, need of the travel
ling public 1t is that each steamer entering
the port of New York be obliged to exhibit proml-
ncntly in her cabin memorandum OF her present
classification at Lloyds the times aud places she has
been ashore stranded, the number and manner of
her collisions and the time and place of change from
sidewhee propeller, II such has taken place. With
these requirements in force owners of steamers will
take pains to have them commanded by most careful
navigators and rigid dscphnarians, and an ocean
voyage, when made on vessel with a clean memo
randum, will be surrounded with the fullest sense OF
security. q. CAMMACK.