Captain Albert E. Theberge, NOAA Corps (ret.)
Published
in: Technical Papers 1989 ASPRS/ACSM Annual Convention
Surveying
and Cartography Volume 5, 1989. Pp. 334-346.
NOAA
Central Library Call No. TA501. A638 1989 Vol. 5.
Page:
1 2
ABSTRACT
Man's
ability to determine the character of the seafloor has been
evolving for over 3500 years. Depictions of Egyptians using
sounding poles and line and sinker sounding methods date to
1800 B.C. These hand-manipulated methods allowed plumbing the
depths to ten's of fathoms. By the first century B.C., this
method was sufficiently advanced that a depth of over one mile
was measured in the Mediterranean. Although various investigators
attempted to make deep-sea soundings, it was not until the 19th
century that the advent of mechanical sounding systems made
deep-sea soundings feasible on a systematic basis. The electronic
echo-sounder was developed in the early 1920's and in its various
versions it has obtained soundings over millions of miles of
survey lines beginning with early investigations off the California
coast. In the 1960's, a revolution in our ability to depict
the seafloor began with the advent of multi-beam swath sounding
systems. Today's bathymetrist has the ability to obtain unprecedented
resolution and coverage of seafloor features with these hull-mounted
systems.
Sounding
Pole and Leadline
The
Classical Period
The
first evidence that man was measuring the depths is found in
tomb paintings of ancient Egypt dating from 1800 B.C. The bas-relief
carvings of Deir al-Bahri were ordered by Queen Hatshepsut to
commemorate a voyage to the land of Punt in approximately 1500
B.C. One of these carvings shows a man using a long slender
pole as a sounding pole on the bow of a large vessel under oar
and sail (Soule 1976). There are also paintings of men taking
deeper soundings by means of a weight attached to a line dating
from this period.
However, the first written account of a line with a weight attached
for sounding did not occur for another millennium. The Greek
historian Herodotus writes of a sounding in 66 feet of water,
far offshore from the mouth of the Nile River, bringing up yellow
mud similar to that deposited on land by the annual flood of
that great river. This brief passage shows that hydrographic
knowledge had evolved to an awareness of regional depths as
well as seafloor characteristics by the 4th century B.C. About
100 B.C., Posidonious lowered a line into the Mediterranean
somewhere between Rome and present day Sardinia. Strabo, a Greek
geographer is quoted: "The sea of Sardinia, than which a deeper
sea has never been sounded, measuring, as it does, according
to Posidonius, about 1,000 fathoms (Soule 1976)." This isolated
incident marks the only successful recorded deep sea sounding
in the entire history of mankind up to that time and remained
so for the next 1900 years.
Approximately 150 years later Acts 27, Verses 27-44 of the New
Testament recounts the shipwreck of Paul on the island of Malta:
"....as
we were drifting across the sea of A'dria, about midnight the
sailors suspected that they were nearing land. 28 So they sounded
and found twenty fathoms; a little farther on they sounded again
and found fifteen fathoms. 29 And fearing that we might run on
the rocks, they let out four anchors from the stern...."
It appears that by the First Century A.D. soundings were taken
regularly while in proximity to the shore. This is also perhaps
the first recorded sounding line. Continuing Acts 27:
...39 Now when it was day, they did not recognize the land,
but they noticed a bay with a beach, on which they planned if
possible to bring the ship ashore... then hoisting the foresail
to the wind they made for the beach. 41 But striking a shoal
they ran the vessel aground; the bow stuck and remained immovable,
and the stern was broken up by the surf...
"That
they did not recognize the land" shows that early sailors relied
on the memory of their pilot to effect safe trips. Knowledge of
local coastal configuration resided nowhere but in a pilot's memory
although sailing directions called a periplus did exist by the
First Century A.D. giving general coastal configurations. Depth
information was limited to personal knowledge of a given area
or what the cast of the lead showed as a ship approached shore.
Going to the fourth century A.D. there was a famous Indian pilot
named Suparaga who "knew the course of the stars and could always
readily orient himself; he also had a deep knowledge of the
value of signs, whether regular, accidental, or abnormal, of
good and bad weather. He distinguished the regions of the ocean
by the fish, by the color of the water, by the nature of the
bottom, by the birds, the mountains [land marks] and other indications"
(Needham 1971). It would seem that the ways of the sailor in
the East where the same as those in the West.
The
Awakening
For the next thousand years little changed for the mariners
of the world with respect to depth-finding, navigation, and
charting. Technology slowly moved ahead with the introduction
of the magnetic compass in the 12th century to western seafarers,
the development of the portolano pilot guides with the accompanying
portolano charts in the thirteenth century, and improvements
to navigational instruments. In the early fifteenth century,
Prince Henry the Navigator founded the first school for navigation
at Sagres, Portugal, on the southwest promontory of Europe.
This resulted in the development of the lateen-rigged caravelles
(a new type of vessel which allowed sailing closer to the wind
than the old square-rigged vessels) which literally explored
the world and fostered many other new developments in navigation
and technology. Most importantly, Prince Henry brought scientific
methodology and the concept of systematic mapping and exploration
to the trades of the mariner and chartmaker.
Africa was rounded and the Americas discovered but the mariner`s
primary sounding tool remained the leadline. Routers or rutters
of the sea (similar to today's Coast Pilots or sailing guides),
such as the famous Hastings Manuscript of the late 15th Century,
were much improved in quality from the early portolanos and
by 1584 Lucas Jans Waghenaer of Holland had published his famous
atlas Spiegel der Zeevaert which included some of the
earliest charts showing actual depths. His name was commemorated
by the term "waggoner" which was synonymous with pilot guide
for centuries.
The state of knowledge of the coastal waters of Western Europe
at this time is epitomized by the account of Master Jackman
on Sir Martin Frobisher's return voyage to England in 1578.
Using an armed lead (these have a socket filled with wax or
tallow to pick up bottom samples), he 'sounded and had 70 faddems,
oosy sand, whereby we judged us to be northwards of Scilly,
and afterward sailed south east all that night'. The ship rounded
Lands End safely, and in three days 'had sight of the Start,
5 leags off, God be praysed!" (Morison 1971).
During this time many rutters were being published such as William
Bourne's, who wrote in 1574 "Also it behoueth him to be a good
coaster, that is to say, to knowe every place by the sight thereof"
(Morison 1971). Rutters also included information (sometimes
ad nauseam) on the character of the bottom. A typical passage
in the earliest English sailing directions refer to "sandy wose
and black fishey stonys .... redd sande and black stonys and
white shellis .... grete stremy grounde with white shellis ...
the grounde is redd sonde and white shellis amonge .... the
grounde is white sonde and white shellis". That there were fine
arguments as to which white shellis were which as suggested
in Survey of the Seas (Blewitt 1957) is corroborated by an account
of the "Ship Hopewell from Newfoundland bound for London in
August 1587 `drawing neere the coast of England' sounded and
found seventy fathom, but nobody could agree on interpreting
what the lead brought up; so through `evil marinership were
fain to dance the hay foure days together' running northeast,
southeast, east, and east-northeast" (to dance the hay refers
to a folk dance in which the participants moved in circles)
until finally sighting a known point on land (Morison 1971).
Although sounding technology did not significantly improve,
advances in surveying and charting the depths continued over
the next two hundred years. In 1647 Robert Dudley's atlas, 'Dell
Arcano del Mare (Secrets of the Sea), was published posthumously.
This work was well ahead of its time with all of its charts
being constructed with the Mercator projection as well as being
the first charts with printed depths on the east coast of North
America. Numerous navigation instruments were designed and with
the development of the chronometer, longitude was now within
the grasp of the surveyor and navigator. The principles of triangulation
were being applied to the problem of surveying at sea beginning
in 1747 with Murdoch MacKenzie (Senior) working on the coast
of the British Isles. James Cook independently discovered this
method and used triangulation extensively for land control in
his great survey of Newfoundland. Indeed, Cook's work is considered
to be the first scientific large-scale hydrographic survey ever
to be carried out (Blewitt 1957).
Interest in deep-sea soundings began during this period. On
September 4, 1773, Captain Constantine John Phipps lowered a
line with a 150-pound weight attached from H.M.S. RACEHORSE
into the Norwegian Sea. He sounded and found 683 fathoms with
a very fine blue soft clay bottom (Deacon 1962). It is noted
that Ferdinand Magellan attempted to sound off the Unfortunate
Islands (present-day Puka-Puka in the Tuamotu Archipelago) on
January 24, 1521, and found no bottom (Morison 1978). Various
accounts state that he put out anywhere from 200 to 750 fathoms
of line before giving up.
Improved
Mechanical Sounding Devices
Charles Wilkes
|
Following
Phipps' sounding, the next milestones in deep-ocean sounding
occurred six decades
later. Charles
Wilkes, while leading the United States Exploring Expedition
(1838-1842), was the first to attempt using wire as opposed
to heavy rope for sounding. Because Wilkes used copper wire,
the tendency of the line to break, kink, and snarl far overcame
any speed of sounding increase. As a consequence Wilkes gave
up, although his first sounding on the Antarctic shelf in 320
fathoms was with copper wire (Stanton 1975). In 1840 Sir James
Clark Ross conducted the first open ocean deep-water sounding
in 2425 fathoms in the South Atlantic at Latitude 27o
26'S, Longitude 17o 29'W (Deacon 1962). Deep-ocean
sounding was given added impetus by the desire to lay a Trans-Atlantic
cable. By the mid 1850's sufficient depth information had been
acquired that Lieutenant Matthew Fontaine Maury, the "Pathfinder
of the Seas", was able to publish the first bathymetric map
of the North Atlantic Ocean basin. However, many of the soundings
on this map were erroneous and, coupled with the paucity of
data, led to missing of some major features and the delineation
of some features that did not exist.
Mechanical
sounding instruments took a leap forward in 1872 with the invention
of a sounding machine using small diameter pianoforte wire.
This machine was introduced by Sir William Thomson (later Lord
Kelvin). In 1872, Sir William made a test of this instrument
from his private yacht the LALLA ROOKH, and described this first
successful wireline sounding: "When from two thousand to twenty-five
hundred fathoms were running off the wheel, I began to have
some misgivings of my estimation of weight and application of
resistance to the sounding-wheel. But after a minute or two
more during which I was feeling more and more anxious, the wheel
suddenly stopped revolving, as I had expected it to do a good
deal sooner. The impression on the men engaged was that something
had broken, and nobody on board, except myself had, I believe,
the slightest faith that the bottom had been reached.... until
the brass tube with valve was unscrewed from the sinker and
showed an abundant specimen of soft gray ooze.... That one trial
was quite enough to show that the difficulties which had seemed
to make the idea of sounding by wire a mere impracticable piece
of theory have been altogether got over" (Agassiz 1888).
Sir William Thomson also invented the pressure tube method of
sounding which became known as "self-acting sounding" (U.S.
Naval Hydrographic Office 1962). This method allowed the ship
to continue steaming while dropping the sounding tube over the
side. It used a long sinker equipped with tubes lined with silver
chromate. The compression of the air in the tubes indicated
by the white line of the silver chromate, was a measure of water
depth. By 1888 the steamer BRITANNIC had sounded using this
method in one hundred and thirty fathoms over the Newfoundland
Banks while cruising at sixteen knots (Agassiz 1888).
Although Sir William invented the pianoforte wireline sounding
instrument and provided the great CHALLENGER expedition with
his instrument, the British naturalists chose to use the Baillie
sounding machine, a fibre-line machine using hemp No.1 line
weighing 200 pounds to the nautical mile, for the 363 soundings
taken during the four-year expedition. It remained to the Americans
to perfect the use of wire sounding (Tanner 1897).
The U.S.S. TUSCARORA, sailing a few months after the CHALLENGER,
undertook a cable survey from California to Japan. At the direction
of Commodore Ammen, Chief of the Bureau of Navigation, the TUSCARORA
was outfitted with a Thomson machine. Captain George E. Belknap,
commanding officer of the TUSCARORA, successfully used the wire
sounding machine for this survey. After this success, a Thomson
machine was installed on the Coast Survey Steamer BLAKE which
was used to delineate the Gulf of Mexico, much of our Atlantic
continental shelf and slope, and much of the Caribbean. Lieutenant
Commander Charles D. Sigsbee significantly improved and modified
the Thomson machine (sufficiently to have the machine christened
the Sigsbee sounding machine) and also directed the survey of
the Gulf of Mexico, which resulted in the first truly modern
bathymetric map.
Tanner
Sounding Machine
|
One
other notable name in deep-sea sounding
during
this period is that of Commander Zera Luther Tanner, USN. He
was commanding officer of the United States Fish Commission
Steamer ALBATROSS for eleven and a half years. During this period,
the ALBATROSS worked from the U.S. East Coast to the Bering
Sea doing fisheries surveys, deep sea dredging, and cable surveys
such as one from California to Hawaii. Commander Tanner invented
a shallow water wire sounding machine called the Tanner sounding
machine and many other oceanographic instruments.
Many variations of the wireline sounding machine were developed
over the next 50 years, most notably the Lucas Sounding Machine
which was primarily used on British ships and the LL type and
Deep-sea sounding machines used by the Coast and Geodetic Survey
(C&GS). The wireline machines delineated the major features
of the ocean basins of the world including many of the trenches,
rises, and continental slopes we know today. Notable successes
included: further delineation of Maury's "Telegraphic Plateau";
the surveys of the Caribbean Sea and Gulf of Mexico by the BLAKE
and ALBATROSS; valid soundings of 9636 meters by the U.S.S.
NERO in the Challenger Deep (Mariana Trench); 8525 meters in
the Nares Deep (taken in Puerto Rico Trench) taken by the U.S.S.
DOLPHIN in 1902; and 8513 meters in the Tuscarora Deep (Kurile
Trench) taken by the U.S.S. TUSCARORA in 1874. As impressive
as these successes were, it is well to remember that Sir John
Murray, one of the outstanding oceanographers of the late Nineteenth
and early Twentieth centuries, compiled only 5969 soundings
in depths greater than 1000 fathoms by 1912 (Murray 1912). Deep
ocean sounding by mechanical means remained a painfully slow
process. Fortunately for the oceanographic community, a new
method was being developed.