The Key West citizen. [volume] (Key West, Fla.) 1879-current, 1938-11-26
Mccarthy Reviews $25O,OO0
Florida Keys Survey Work
Coast And Geodetic Survey
Reveals Amazing Story
In TOpOgraphics, Hydro
graphics OF Islands

Coast and Geodetic Survey work
in mapping the land and water
areas of the spreading, curving
Florida Keys was told The Citi-
zen today by Lieut. E. r. McCar-
thy, officer in charge, with Off
ces at the post office building.
Most amazing is the story of the
natural building of the channels,
flats, lakes and beaches. From
Key Largo down to Matecumbe
the reef is solid line along the
coast. Then follows the wide
sweep of water known as the
water gap" along Bahia Honda
where the channel comes through
about three and a half miles an
hour. The reefs then begin to
multiply again around American
Shoals light. Whenever there is
an open sweep of sea, beaches
spring up on shore. Beach sand
is found back as much as a mile
or SO from the water wnen the
shoulder advanced. Off Key West
the reef and shoals are pretty
much broken up and that is their
reason for some of the beaches
here. Along the Boulevard traces
of beautiful beaches were found.
Lieut.. Mccarthy said.
With the reefs springing up
bottom grass and mangrove roots
made solid ground eventually.
When the islands" thus sprang
up the different tides pouring in
between them from the Gulf and
Ocean then formed natural chan
nels. At some spots not more
than five miles apart one can find
high tide and low tide. As the
tides come together and mix they
deposit sand, as their carrying
power" is lost, and more islands
and sand banks are formed. There
is a six foot tide at Harbor Key,
the greatest of the keys.
Changes of the Florida Keys
are extremely rapid. Lieut.. Nc
earthly said. Since the survey of
10000 he found differences of
500 feet of land in some places.
Little lakes are continually filling
up. Hurricanes rip up places
when water is held back by gaps,
but in the Labor Day hurricane
at Matecurnbe the water went
over the top so the beach there
was not damaged In some hur-
ficane ravaged beaches remains
of other beaches are found un-
usual layers below.
Airplane Maps
In the work an airplane topo-
graphic map is the first taken. A
five lens camera shows five views
of the land below. The scale is
10000. Each five view map
represents an area Q miles long.
On this map Geodetic officers can
then pick out coconut trees. flats.
mangrove bushes, lakes. shallow
and deep water, beaches, cham
neis and other types Of land vege-
tation of the keys. As for types
Of water bottoms there are most
IN sand. rock. mud and grass. All
are marked on the charts.
Then follows the field work in
which soundings are taken at
three second intervals of all the
low water" of the keys. The
deep water Soundings viii be
taken by ships of the Coast and
Geodelic Survey later. In order
to situate the maps in the proper
latitude and longitude and make
the correct scale of miles, first a
..gcoid' or a plot of the shape of
the earth along the Keys Is made.
EAbUt Wis ktHkN Tit N0tANSe Wi
gitudinai and latitudinal positions
may be determined. Then follows
the triangular towers erected
along the KEYS. a familiar sight
BY the system of triangulation,
angles and triangleS. distances
and positions may be determined.
A magnetic cheek is also made.
Thus are the keys placed proper
b on the charts. Lieut.. McCar-
thy in his field trips among the
mangraves and swampS has never
seen a rattlesnake, His advice is
"juSt don't look for them and
you'll come out all right"
All Of Monroe county has been
completely surveyed Lieut., Nc
earthly told The Citizen except
the section more than five miles
inland in the Cape Sable region.
and another section on the lower
keys. The work began in August.
Continued on Page Six