The southern press. [volume] (Washington City [i.e. Washington, D.C.]) 1850-1852, 1851-05-07


HEiaHr Asr Powta or WAvEs.-Thefe d
great diversity of opinion among scientific men,
about the height to which waves are sometimes
rolled up In d storm. We saw it stated in some
journal, but few days since, that waves never
run more than ten feet high, while Humboldt,
in his Cosmos, estimates their extreme altitude
at twenty-five feet Recently, however, q more
careful investigation of the phenomena of waves
has been instituted, which shows results en-
tirely Mt variance with the estimates We have
mentioned, and more in accordance with the
popular idea of waves rolling mountains high.
Dr. Scoresby, in paper read before the Brit
ish association at Edinburg, has thrown much
light upon this interesting inquiry. His re-
searches, an account Of which we find in the
Boston Journal, were conducted during two At
antic voyages in a steamship, under circum-
stances very favorable for observation. by an
examination instituted during n hard gale, he
found that the average height Of the waves was
full fifteen feet and upwards, and the mean high
est waves about forty-three feet above the level
of the hollow. He also found that after storm
of about thirty-six hours duration, which had
abated several hours before the observation, so
that the waves had perceptbly subsidized, waves
were noticed OF twenty-six feet average eleya-
ton from ridge to hollow, and even of thirty
feet They were, however, OF no great extent
on the ridge.
When waves meet with an obstruction, their
height is increased. AT recent meeting of the
British Association, Thomas Stevenson, esq,
civil engineer, gave the results of some careful
observations made at the Bell Rock lighthouse,
from which it appears that on the 20th Novem-
Der, lS47, in heavy ground swell, alters storm,
solid waterr rose at the Bell Rock lighthouse one
hundred and sic feet above the level of the sea.
.If we recollect right" says the print from
which we have quoted, :. the waves have been
known to dash up the sides Of the Eddystone
light, to the height Of the lantern which is over
one hundred Net above the rock We are in
formed by Mr.. Bennett, the keeper of the light
house late on Mnot's Rock, that he has known
the waves TO rise at that structure above the
couplings of the piles, which were thirty FIVE feet
above the rock, and about twenty-five above the
high water mark.
Here, however, the piles Of the lighthouse
offered but small resistance to the waves CON-
pared with a solid structure, and the only thing
which would be likely to raise the water above
the usual level, is its striking against the rock
ITSELF This, however, berg several feet below
the level of high water, would tend rather to
break the waves than to increase their height
There is good reason to believe that during the
recent storm which destroyed the lighthouse,
the waves struck the store-room, the bottom Of
which was forty-seven feet above the rock, and
allowing five feet extra for the extraordinary
rise of the tide, thirtytwo feet above high water
mark.
aThe length and velocity of waves vary. In
rounding the Cape of Good Hope, waves, are
not unfrequently met with, so vast, that few
ridges and few depressions occupy the extent
of mile. These waves propagate their motion
at the rate of thirty or forty miles per hour. Mr..
A. G.. Findley, in paper read before the Society
Of Arts, stated that waves Of from three hundred
to four hundred feet in length from crest, travel
with velocity of twenty to twenty seven and
one-half miles per hour, whether they are fifty
or fifty-four feet in total height. They travel
for great distances, and are often raised by dis
tant hurricanes, having been felt at st. Helena
and Ascension, which are six hundred miles
apart; and he remarked that it is probable that !.
ground swells often originate at the Cape of
Good Hone, a distance of three thousand miles.
Dr. Scoresby, to whose investigation we have
already alluded, carefully estimated, the velocity
Of the waves, and found it to be at the rate of
80. 81 Engl h statute miles per hour. He est
mated $50 feet rs the probable mean distance
of the waves, or the width passed over between
crest
pose that the water advances with the wave. 1t
is the form only which advances, the water ris-
ing and fall ng in the same place, except when
II reaches beach, when il becomes really pro-
pressive from the f,ct that il cannatTink direct
Nv down, and therefore falls over forward.
aThese statements in relation to The height
and velocity of waves have perhaps prepared our
readers to estimate. with some degree of correct
ness. their force. When we see column of
water, at least thirty feet in height, advancing
with the speed of railroad train, we can readily
imagine that its force is almost irresistible. We
have already mentioned the Investigations of
Mr.. Stevenson. His observations on the force
of the waves, made by him with reference to the
construction Of marine works, are of much i'm
terest and importance. These observations were
made by means Of the marine dynomefer He
found that during a westerly gale on the 29th
March, l845, force of three tons per square
foot was exerted at the Skerryvore lighthouse,
in the Atlantic ocean. In the German ocean, at
the Bell Rock lighthouse, the greatest result
was 3,0l3 pounds, or about one and
n half tons per square foot These results are
astonishing. and it is no wonder that in the en-
counter with such force, the largest chips are
but TOYS. and wood and iron almost as fragile rs
glass. Nothing but stone can be expected 10 |
resist such force, and that must be rs firmly
fastened ss the lodges on which the waves spend
their fury"
The following additional facts about light !
houses, which may be intering in this connection,
are reported in the London Aahencum
aThe Eddystone lighthouse, having been
built Of wood in 1893, was carried away five
wears after its erection. IL was shortly after |
wards reconstructed Of the same material, the
lower part being filed with stone or concrete;
Il then lasted for forty years, when ii was con-
sumed by fire. In 1859, Smeaton completed the
present lighthouse, which is 6S feet high, and the
base 26 feet in diameter, (being barely less than
the surfsce of the'rock on which II stands) Itl
is built Of stone; the stones are dovetailed 10
cether, and "joggled" rs IL is termed. so as to
prevent the courses of stones from sliding on
each other. Il is situated in the midst Of the
sea, nine or ten miles distant from Plymouth.
The Bedrock lighthouse stands on rock Of
the same name on the east coast Of Scotland |
II is surrounded by the and is 100 feet high.
and AZ feet in diameter at the base. II was
built by Robert Stevenson, and finished in 1910.
Its trucfior ia similar 10 that Of the Eddy.