Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1890-12-16


to the square foot. No doubt III 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 adj
vance, even when their dimensions are
small. A wave 200 feet in length, from
hollow to hollow, has velocity OF ~
knots an hour, and such wave are OF
common occurrence. 4 wave 400 feet
in length has velocity OF u knots an
hour, and IN Atlantic storm-waye 600
feet long moves at q speed OF
32 knots an hour. In consider
ing the subject of the velocity Of
waves ii should be borne IN mind,
however, that in all wave motion it IL
the wave form which travels at these
high speeds, aud not the particles OF
water. This has been satisfactorily
proven, both by observation aud expert
ment. II a billet of wood is dropped
overheard from a ship. past which waves
are travelling at great speed, it well
known that it is not swept away, rs 1t
would be on tideway where the parti-
Giles OF water moved onward. but it SIM
ply sways backward and forward as sue
cessiye 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 ascer-
tainsble relation to their magnitude and
the depth OF water over which they pass.
1t has been calculated by Airy that a
wave 100 feet in breadth, and in water
100 feet deep, travels at the rate of about
fifteen miles an hour; one 1000 feet
broad, and in water 600 feet deep, at the
rate Of forty-eight miles one 10000 feet
in breadth, and in water 1910 feet deep,
will sweep forward with a velocity of not
less than 15i miles al hour. Bache
stated as one of the effects OF an earth
quake at Samoda, on the island Of
Nippon, in Japan, that the harb6r 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-actlng 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 1t had
receded from the harbor Of Samoda.
Hence 1t had travelled across the broad
bosom OF the Pacific Ocean at the rate
Of 81 miles minute.
Carefully repeated experiments made
by an experienced English navigator nj
Santander. on the north coast OF Spain,
showed the crest of the sea waves IN a
prolonged and heavy gale Of wind TO he
~ feet high and allowing the same for
the depth between the waves, the result
would be a height of "a feet from crest
20 hollow. The distance from crest to
crest was found to he 1856 feet. Estimates
Of the waves in the South Atlantic during
great storms give a 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 Aarslli, in IN:
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 tC
hollow. No douDt this height has been
exceeded at times, although the Medi'
| terranean is by no meansnoted for heavy
seas. The Gallia, IN "A voyage 70 New
| York last January, was boarded by a sea
that her captain estimated was 100 feet
| l. .al
Gallia been boarded by another such seG
she would have foundered inevitably.
AS 10 the ratio Of the heights to the
lengths observed in deep-sea waves, au
thorlties agree that rs the lengths in
crease this ratio diminishes. and the
wave slope becomes less steep. TIT
shortest waves are the steepest, and the
greatest recorded inclinatonsare for very
short waves, when the ratio of heighth
10 length Was about | TO &. For waves
from $50 TO $50 feet in length the ratio
of to has been observed, but these
were exceptionally steep waves; FOL
waves 500 to 600 feet in length it falls tC
about to 20, and for the longest waves
it is said to fall az low as TO 80.
1t seems probable that in waves OF the
largest size commonly me. the height
does not exceed one-twentieth of the
length, and the highest limit of steep
ness in waves which are large enough tC
to influence considerably the behavior Of
ships does not give ratio of height
exceeding to 10. Waves from 500 to
900 feet in length are sometimes en-
countered having heights of from > to II
feet only.