N. H. Heck,
U. S. Coast and Geodetic Survey
(From
the U.S. Coast and Geodetic Survey
ASSOCIATION
OF FIELD ENGINEERS BULLETIN
no.
3, June 1931)
At present
there is not much wire drag work being done as some years ago,
partly
because the more important work is finished and partly because
of lack of funds to undertake the remaining work.
There
are still large areas where the use of the method is indispensable
for the safety of navigation. Other methods will probably
develop the existence of most shoals, but some may be missed
and more likely the least depth, which is the thing the
mariner cares most about, will be missed.
I have
seen a rocky pinnacle charted as an 11 fathom shoal
become, after four successive groundings of the drag, each
time set so as to pass over the least depth previously found,
an 11 foot shoal. Each time a more careful sounding
than customary in the most careful hydrography when the
drag is not used was made with the additional advantage
of having the drag buoys as a guide, and yet the sharp pinnacles
were missed. I have been on a coral reef in Porto Rico (sic),
with general depths of about two fathoms and perfectly clear
view of the bottom, and swung a leadline at 11 feet within
6 inches of a 5-foot coral projection without touching it.
In view
of these considerations, some reminiscences about past occurrences
during the period when I was on this work may be of interest.
Back in 1904
when the work started, a number of vessels of the Navy, using
Penobscot Bay for maneuvering, had struck bottom, and striking
the granite rocks of Maine leaves a very definite impression.
A number of yachts en route for Bar Harbor struck bottom in
an important channel. The first attempt to meet the situation
was with the pipe drag, by which method a 36-foot pipe was carried
below the vessel, which proceeded at a moderate speed. Some
important findings were made, but the method was clumsy and
expensive on account of the overhead of the vessel and the frequent
need for repairs to apparatus. I spent one season under Captain
Faris on this work on the EXPLORER. The same objection of too
great overhead applied to the first season of wire drag in Frenchmans
Bay when launches of the BACHE and the BLAKE were used with
the vessels standing by much of the time. Several years later
the first wire drag work by a wire drag party, independent of
vessels, was started in Eggemoggin Reach, Maine, under my direction.
Our first effort was to prove the deep water clear and all known
shoals were carefully avoided. As a result, we made fast progress
and startled the office by telegraphic request for another smooth
sheet before the season was half over. Curiously enough six
years later we went over this same region examining the shoals
and finding a considerable number of important dangers.
Wiredrag operations in Southeast Alaskas - 1920's
|
The development
of the wire drag was a long story, with many persons taking
part, but in those days few of our personnel realized the scientific
possibilities which have since been developed in our hydrographic
work. It was a matter of search for materials, inventions and
application of new methods just as is going on to-day in the
acoustic work. For example, we first used telephone wire, which
did very well, but invariably broke when we struck bottom. We
found a wire developed first by Krupps in Germany and later
improved by Roebling which met all requirements.
Many
interesting things happened in this work. For example, there
was the project of the so-called Beehler Channel into Key
West. Commodore Beehler was Commandant at the Naval Station
at Key West and he conceived the idea that a straight channel
might replace the existing main ship channel. I received
instructions to test out this possibility. The difficulty
at Key West is to pass the inner reef, a mass of mushroom-shaped
coral heads and other formations extending 16 to 20 feet
above an otherwise flat bottom and in many places as thick
as the trees of a forest. The idea turned out to be quite
impossible, but one day we thought we had found a channel.
Approaching the reef with the intention of finding the obstructions
on a given line, and using a 500-foot drag, it became very
hazy and just as we came to the reef, we were unable to
get a position. When we finally got a position we had passed
through the reef. We tried to repeat the performance and
found it quite impossible. We must have missed by inches
at least six of the large coral heads. In the main channel
we found a pinnacle which might have changed history. It
was directly in the channel and the MAINE might easily have
struck it when outward bound in her start for Havana. We
caught the drag on this several times and the divers who
placed the dynamite for the Army engineers to remove it
found several large wire drag sinkers and various wires
festooned around it. When coral heads are blown up the pulpy
inner portion floats and looks very much like pumice.
One day
we encountered a very strong current in a place where strong
currents had never before been noted. There were no particular
indications of bad weather, but that night a very heavy
norther arrived, showing that in the Keys lying between
the Gulf of Mexico and the Straits of Florida barometric
conditions may have powerful effects even before their existence
is realized.
On one
occasion in Maine a sub-party under Mr. Swick (now mathematician
in the Division of Geodesy) was searching for a reported
shoal off Penobscot Bay directly in the path of battleships
going to the Rockland trial course. He had to give up work
because of the large number of lobster pots and had to make
the search later. However, since the area had not yet been
reached in the regular survey, Mr. Swick decided to run
a line in the homeward bound direction to make it a full
working day. He had just decided to call it a day when the
signals were temporarily obscured and a fix was delayed.
Just as they became clear, the drag went aground. A 22-foot
rock, not even known locally to exist, was found, and of
course, charted, but not buoyed. Some years later the battleship
ARKANSAS, not yet accepted but en route to the trial course,
was proceeding with a local pilot. The vessel struck this
rock, and on examining the pilot's chart, it was found that
his chart was old and did not show the rock. That he was
a good pilot otherwise was proved by the fact that the rock
plotted exactly on the course he had laid out on his chart.
However, the answer was $80,000 worth of damage and considerable
delay in the delivery of the vessel.
That
the newspaper man can often see interest in what appears
to be very routine to us was never better exemplified than
by the performance of a writer of the Boston Transcript.
He went out one day and, to my view, it was a day of very
routine character, but he wrote up as interesting an account
of an operation of the Coast and Geodetic Survey as has
ever been written.
Perhaps
the most striking thing that happened was the development
of the wire sweep. After returning from England from special
duty with the Admiralty on anti-submarine devices during
the War, I spent several months at the New London Naval
Experimental Station (the forerunner of the present Naval
Research Laboratory in Anacostia) before returning to duty
in the Coast and Geodetic Survey. During this period we
were all trying to see what application could be made of
the war time devices. One day it occurred to me that, with
modification, the mine sweep principle might be applied
to wire drag work. I simply put the idea away for future
reference. After some interesting duty in Lake Washington,
Seattle, locating the trees of a forest which, perhaps a
thousand years ago, sank beneath the lake in almost vertical
position and were an obstruction to navigation, I was assigned
to command of the EXPLORER on wire drag and combined operations
in Southeast Alaska. We found on hand a large amount of
buoys, metal floats and other materials hastily stored by
Messrs. Colbert and Daniels when they discontinued work
to enter the Navy. Much of this material was obviously in
bad condition, but we selected a considerable amount which
seemed to be all right. We started work with a drag 12,000
feet in length and the first day went all right. The second
day just as we were about to start work the entire drag
with most of our wire drag equipment except wire, of which
we had an ample supply, sank beneath the surface in perhaps
two minutes' time. All the buoys and floats were crushed.
It looked bad for our season's work and Mr. Senior, Executive
Officer, and Mr. G. C. Jones, who was in charge of the drag
work, had gloomy faces. I saw only one thing to do - try
out the sweep idea and use gasoline drums for buoys. We
put rounded wooden bottoms on them to partially streamline
them and later found means to pump air into them. This worked
out so well that, while we ordered no more equipment, the
season's output was the largest to date for Alaska and,
in fact, the wire sweep work went so fast that it was hard
to keep it from getting ahead of the control. This speeding
up resulted in finishing the important work of sweeping
the main channels of Southeastern Alaska by several years
over estimated time.
Since
the sweep wire was continuous to the vessel and without
a rope section intervening as in the wire drag, an interesting
fact was observed. When the sweep struck a rock, it did
not catch immediately but slipped along while taking its
grip. As a result, the wire acted like a banjo string and
actually a tune was played with varying notes which could
be heard all over the vessel. This is probably the longest
string instrument in existence since on one occasion the
rock was 1 1/4 miles away.
The World
War caused untold loss, but it is interesting to note that
in the work that has been described and in the acoustic
sounding and radio position finding, which are a direct
outcome of war-time developments, we have added and are
adding important amounts to the war salvage.