Every evening, Wilmington daily commercial., 1920-07-13
NEW PHOTOGRAPHIC
SURVEY OFF LEWES
Government Ascertaining Ocean
Bottom Conditions From Fen
wick TO New York.

speriai CORRESPONDENCE OF Every Evening
Icwes. July l3.-The U. ). ). Bache, of
the Coast and Geodetic Survey, a com
posite built steamer OF AZ tons, WIFI
romplement. exclusive Of her commanding
oficcr of eight wardroom officers and
az enlisted men. is in the vicinity of Lewes
until November 10 make complete
photographic survey of the approaches to
Delaware Bay. The project includes a
survey from the Delaware shore out to the
100 fathom curve, distance OF about 20
milcs from the light of Fenwlck Island ana
the Light and Shoals vessel, to the en-
trance of New York harbor. After NO
yembcr. when weather conditions become
such that little field work can be done,
operations in these waters cease untii
kpr,l or Nav. The Bache returns to this
nor, every weekend, arriving about
SATURDAY. noon, and leaving again tor the
working grounds Just outside the capes,
Monday morning.
The Bache is fitted up with all kinds OF
scientific and navigating instruments,
forward is chart room where an expert
records on charts daily soundlngs; huge
buoys tackle and rope literally cover her
deck. and below aft is spacious room Win
office equipment, where the ship eXecu-
tive work Is done. Aft on the mann deck
Is a winch engine, which handles the
sounding line, graded TO fathoms ana ieet
and 50 read. An ordinary hand line with
~ pounds Of lead is used for soundngs up
10 Is fathoms; between II and % fathoms
a 2O or o pound lead line is used. Be
yond 25 fathoms an electric sounding ma
chine is used. The lead is fastened to a
traveller near the s,crn and runs forward
BY gravi,y 20 point near the bow, where
il r automatically released. The leads
man reads the line when the ship has mov-
ed forward To the point where the lead
was released The line is hauled IN taught,
straight up and down and depths ascer-
tanned. Soundings are made at five miles
an hour.
The Bache steams out to sea, picks out
three stationer objects on shore for sig
mails. and through two-section angle
instrument, figures out its position by
rrigonometry, each day resuming its
work exactly where it left of the day be
fore. There is also aboard three-arm
tractor or station pointer, which graphic
ally determines the ships position.
These shore signals can be observed ten
miles: beyond that limit. survey buoys are
anchored for signals, which are placed
three miles apart and parallel with the
shore line. Using these buoy signals, II Is
possible TO continue the fixed position
work a distance Of about SIX mics beyond
the limit Of visibility of shore signals. ne
ship will then steam for miles IN straight
line. and as soundings are taken an Instru-
ment punctures on charts, the depth oi
water Twenty-four hours Is a working
dav with night shifts. As the work pro-
grcsscS these charts show parallel dotted
lines with onc-fourth-rnile space between
out 10 10 fathoms, which indicates the
route surveyed For the work beyond these
huoys 10 the l0O-fathom curve, the method
Is what is known as precise dead reckon
ing Currents are observed at intervals OF
two hours on the line and an average cur
rent applied TO the compass course which
gives the dead reckoning OF the ship for a
two-hours run. The run to the lOO-fathOm
curve and return Is continued by these
two-hour runs until the position of the
snip can be accurately determined at the
end line.
Soundngs are reduced to mean sea !
level and finally placed on the charts OF the /
coast Unless taken at low water little |
more water in a gwen locality Will be /
found than the charts show.
THE WORK AND WHAT 1T MEANS.
In explaining the work of the Coast |
md Geodetic Service, Commander Seran |
II the Baehe said to Every Evenings cor
'Our primary work Is TO cause an ac- /
,urate survey and maps thereof to be !
made Of the shore line Of the United States. |
Ihis work started with the administration |
4 President Thomas Jefferson, and the /
irst work was done IN 1916. At that time /
our officers were engaged on the work. /
II =
nissioned officers, about 700 enlisted men ,
md hands, and the work Is extended from |
hore line Of the United States to include |
he Philippine Islands, Porto Rico and /
hawaiian Islands and Alaska. The work 1
: both along shore and inland. Principal /
hore work consists IN topographic and I
surveys. fopographing |
urveylng Is merely the mapping Of the i
and the same as YOU will see IN any or I
linary map. photographic surveys are
imply surveys OF the water. To enable the
mariner 10 avoid dangers and revent his /
alhng on the beach, II Is necessary to |
ave maps of the water and numerous /
The hydrogr 4phic surveys
4 the Coast and Geodetic Survey have
zen carried TO such degree of accuracy |
hat il is easily possible for a mariner
rhen making land fall TO sound at in
ervals of about 10 minutes, and in the
curse Of an hour TO be able TO determine
airly accurately his position. The com
ination Of line of soundings and the
adio direction finder, make navigation
luch safer than was ever considered
ossible 30 years ago
The men for this service are enlisted
n period Of one year, with the privilege
obtaining their release on one months
Office, or sooner if a satisfactory substi-
ute is provided. The pay Of the men is
Sactly the same as that received in the
ierchant service
The work Is usually along the northern
past IN the summer months and along
De southern coasts in winter.