Weekly national intelligencer., 1850-03-23
SMITHSONIAN LECTURES.

Lieut. DAVIS United States Navy has Just finished the
Smithsonian Institution, very instructive of Lectures
on the TDEs, This gentleman, to whom the Secretary of
the Navy has assigned the Supernendence Of the United
States Nautical Almanac, fr several years of the
chiefs Of the hydographca department Of the United States
Coast Survey under the direction Of Professor A. D. BAeHE.
In this employment he studied with much attention the
ton of the tides along coast and in the course OF his
lectures the results Of his Investigations series OF in
eresting facts ard deductions Among these may notice
the following Changes constantly going along our
of the utmost importance to the commerce and navga
lion OF our country Al Sandy Hook, example, il well
known that where there is dry land there in 1886
forty fee, Of water and this in the main ship channel In
1867 there was an open channel from Bansabe bay to the
ocean, and as late as the beginning Of this century, heavy
storms the sea occasionally made breach place.
but the process of construction under the law of tidal acon
as explained by the lecturer has closed up this opening
rey and the place is important part Of Cape Cod
Other we'll authencated instances, derived from compa
oD of the recent surveys with the earliest charts OF our coast
were mentioned For example, Monomy Point constantly
extending to the south Under the operation Of the tides,
number Of harbors and ines particularly along Marhas
VINEYARD and Long Island have been gradually closed and
converted into ponds The remarkable fact was stated that
the salt water of these ponds had given place. in the Of
few wears to fresh water Another remarkable fact that
the bottom of these ponds frequently deeper than the bot
tom Of the adjoining This fact is interesting since it
is found that the inhabited part Of sandy deserts such the
oases of the Of Sahars similar depressons the
bottom Of the valley beng instances, below the pre-
sent level of the sea- The lecturer also stated that these
ponds in the of the change become the home in
cession Of salt water brah water and fresh water animals
and thus afford beautiful demonstration Of the geological for
nation of basins such those of London and Paris, in
which the remains of Of animals found in
a fossil state.
Lieut. DAVIS has deduced from his numerous observations
the law Of tidal deposesnamey, that all deposcs on the
external coast are made by the incoming foodtde and
that the increase of depoe always the line of the motion
Of the tidal current Thus, if the tide to the north
along any par, of the coast projecting points, which may
serve as nuclei are found eonga north and south d.
ection This action is confined TO coasts but Lieut.
Davis applies the explanation Of phenomena noticed IN the
Landes of France and Holland.
Another imp ortant deduction is that the depostes at the
mouths Of harbors and esuaes no rver known by the
name of bars are formed from materials deposited by the
The action Of the tide is that Of constant deposition
Degradation Of the the effect Of the and storms
Of the ocean The general action Of the meteorological
diminish the height Of continents and to transport their
materials the sea- while the action Of the tide just the
verse; and tends to keep and preserve around the coast the
materials which have brought down geological periods
In this way the belts Of land which skirt coast have been
thrown up and Long Island itself has probably been
formed in the same way