The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1890-12-27

the cowl OF the chimney over the lamp,
which is about $50 feet above sea level,
and ran in streams to the bottom.
Some experiments have been made with
a view accurately to measure the force eX-
erted by waves The instrument is called
marine dynamometer 1t has a known
surface for the water to impinge on, the
force of the impact being transferred to
springs of known strengths. The distance
to which the springs are compressed is self
registering. This instrument has recorded
the force of the waves, not under extraor-
binary circumstances, as high as three IONS
to the square foot. No doubt in excep-
tional cases the pressure has been more
than double that figure.
Any one observing ocean waves cannot
fail to be struck with their rapid advance,
even when their dimensions are small. A
wave 200 feet in length, from hollow to
hollow, has velocity of 10 knots an hour,
and such waves are of common occurrence.
A wave 400 feet in length has velocity
of ~ knots an hour, and an Atlantic storm
wave 600 feet long moves at a speed of b
knots an hour. In considering the subject
Of the velocity of waves it should be borne
in mind, however, that in all wave motion
it is the wave form which travels at these
high speeds, and not the particles of water
This has been satisfactorily proven, both
by observation and experiment. fla billet
of wood is dropped overheard from a ship,
past which waves are travelling at great
speed, it is well known that it is not swept
away, as it would be on a tideway where
the particles of water moved onward, but it
simply sways backward and forward as sue
cessive waves pass.
INFLUENCE OF THE WIND.
The velocity of waves is said to depend
primarily upon the power and continuance
of the wind, but it is greatly modified by
and bears an ascertainable relation to their
magnitude and the depth of water over
which they pass. 1t has been calculated
by Airy that wave 100 feet in breadth,
AID in water 100 feet deep, travels at the
rate Of about fifteen miles an hour; one
900 feet broad, and in water 900 feet
deep, at the rate of forty-eight miles; one
10000 feet in breadth, and in water TO-
600 feet deep, will sweep forward with
velocity of not less than 1874 miles an hour.
Bache stated as one of the effects of an
earthquake at Samoda, on the island of
Niphon, in Japan, that the harbor was
first emptied Of water, and there came in
an enormous wave, which receded and left
the harbor dry. This occurred several
times. The self-acting tide-register at
San Francisco, which records the rise of
the tide upon cylinders turned by clocks,
showed that at that place, 800 miles from
the scene of the earthquake, the first wave
arrived twelve hours and sixteen minutes
after it had receded from the harbor of
Samoda. Hence it had travelled across
the broad bosom of the Pacific Ocean at
the rate Of 81 miles a minute
Carefully repeated experiments made by
an experienced English navigator at San
lander, on the north coast of Spain, showed
the crest of the sea waves in prolonged
and heavy gale of wind to be ~ feet high;
and allowing the same for the depth between
the waves, the result would be height of
81 feet from crest to hollow. The distance
from crest TO crest was found to be $50
feet. Estimates of the waves in the South
Atlantic during great storms give Il height
of fifty feet for the crests and 400 feet for
length. In the North Sea the height of
crest seldom exceeds ten feet, and the
length $50 feet. The Comte de Marsili,
in his physical History of the Sea, says
that the highest wave observed by him on
the shores of Languedoc, where the fetch
across the Mediterranean was 600 miles,
was thirteen and half feet from crest to
hollow No doubt this height has been
exceeded at times, although the Mediter-
rancan is by no means noted for heavy
seas. The Gallia, in voyage to New
York last January, was boarded by a sea
that her captain estimated was 100 feet
high The captain stated that had the
Gallia been boarded by another such sea
she would have foundered inevitably.
As to the ratio of the heights to the
lengths observed in deep,sea waves, author
tiles agree that as the lengths increase this
ratio diminishes, and the wave slope becomes
less steep. The shortest waves are the
steepest, and the greatest recorded incli-
nations are lOr very snort waves, Wnen the
ratio of heightb to length was about to
g. For waves from $50 to $50 feet in
length the ratio of to s has been observed,
but these were exceptionally steep waves;
for waves 500 to 600 feet in length il falls
to about to 20, and for the longest waves
it is said to fall as low as to so
1t seems probable that in waves of the
largest size commonly met the height does
not exceed one-tweutieth of the length,
and the highest limit of steepness in waves
which are large enough to influence con-
siderably the behavior of ships does not
give ratio of height exceeding to 10.
Waves from 500 to 900 feet in length are
sometimes encountered having heights of
from : to 10 feet only.