Carried out 4 - 10 February 2007
Strandingsmuseum St. George
Measurements with the proton magnetometer
in waters off Tranquebar
Interview with local fishermen
Investigation of masulas and wooden
marine archaeological investigation of the anchorage at
ships lost on their way to and from Tranquebar and East
location with the aqua scan MC5
Measurements of a masula and wooden anchors
Marine archaeological study of the
anchorage and waters off Tranquebar
in India - carried out from 4 to 10
The purpose of the investigation was to locate shipwrecks and other
objects on the seabed or buried
off the coast of Tranquebar. The investigation is to be used as a
preliminary study, which may lead to a larger survey/excavation with Danish and Indian marine
The investigation was initiated by The Tranquebar Association and
carried out by diver Gert
Normann Andersen from JD-Contractor ApS, and technician Kim Schmidt from
HV-Elektro. The Tranquebar Association contacted locals for the use of vessels,
fishermen and divers.
Gert Normann Andersen and Kim Schmidt also represent “Stranding museum
George” (Ringkøbing / Holstebro Museums) in Thorsminde which is
responsible for marine archaeology along the West Coast of Jutland and its fjords.
This rapport will be available on the web pages for Strandingsmuseum St.
) and The Tranquebar Association (
A plan for the preliminary investigations can be seen in appendix I
The primary investigation went largely according to plan. (
Comments and deviations are written in
Before departure from Denmark, a literature search of relevant Danish
and foreign literature was
carried out to get an idea
of what can be expected to
lie in the coastal
waters off Tranquebar. (See
Lawrence V. Mott from Syddansk University wrote, in 2005, a rapport
about the possibilities of
establishing a marine archaeological
(Summer Field School) in
Tranquebar. The rapport
describes the conditions,
and earlier marine investigations in the area.
One discovery is a Dutch ship from the 19th century, which lies at a depth of 23 metres about 5 km
north of Tranquebar. The rapport also describes two circular anomalies near
On the official sea charts from the area, there is a wreck marked
approx. 2.5 nautical miles from
land and approx. 6 nautical miles
north of Fort
Dansborg at a position
of 11 07 191 N and 079 54
Appendix II contains a list of ships belonging to the Danish East India
Company that have been lost
on journeys to East India. There is also a selection of English and
Dutch ships that have been lost along The Coromandel Coast. The number of lost ships is in reality much
greater than listed, as the
lists only include certain periods, and
ships from Spain, Portugal, France and many other
not mentioned. Also local and Asian vessels that have been lost in the area are
not mentioned. A
of literature concerning ships and navigation around India can be found at the
end of the
a point of interest it should be mentioned that many of the foreign ships that
have been lost had
fortunes onboard. Generally the Danish and other foreign ships had large
valuable cargoes from
their homeports. Especially iron and lead were good trading materials in India,
and these were
as ballast during the outward voyage. There were often chests with coins and
gold- and silver bars
that were used to establish and maintain the colonies. Money was also needed to
goods that could be sold for huge profits in Europe. The ships could also carry
crates with weapons,
knives, binoculars and other European articles.
bound the ships were often loaded with silk, dyes, sugar, tea and spices;
which could be sold in Europe for up to 30 times the purchase price in India. Sometimes
carried polished gemstones, ivory and gold from Bengal and other Asian
extracts about lost ships from the British East India Company, there is also
mention of valuable
In the area off Tranquebar there is believed to be the remains of the English
frigate Madras which
sunk with a cargo of coins in 1688. Also the money chest from the
which was lost at sea at Tranquebar during loading in the summer of 1708 should
still be in the
Danish ships, it is expected to find remains of the ships that were broken up
at Tranquebar. Other
ships that were lost along the Coromandel Coast were lost at other locations
both north and south
might also be possible to find remains of masulas, transport boats, which were
used to transport
goods from the ships to the shore.
for our investigations will be based on a systematic search using a proton
This will give us the most accurate positions of shipwrecks and other large
objects at the
bottom of the sea.
equipment is comprised of a probe that is dragged in an underwater cable
approx. 20 metres
the workboat. The cable is connected with an instrument on board the boat where
are set and all the signals can be read (see Appendix III).
proton magnetometer measures the magnetic field in an area. Magnetic fields
differ around the world;
the equipment has to be calibrated by the manufacturer to the specific
location. When iron is located on
the seabed, the magnetic field will be distorted close to it.
old shipwrecks contain iron. These include numerous things from the many iron
rivets; that the wooden
over the whole ship were spiked with, to the anchor, iron fastenings, iron
ballast, canons, weapons and other
equipment on board. Shipwrecks, both old and new, can therefore easily be found
using a proton
Even individual items the size of an anchor or iron canon will give a good
signal, though the
of the signal will not be is as strong as with a whole wreck.
In this way it is easy to tell the
difference between a large wreck and an individual
bottom of an old wooden shipwreck of a reasonable size can normally be measured
at a distance
of about 100 meters on each side of the probe. Most of the old ships that
have located around the world have been with a proton
investigations were carried out from a
open fishing boat. Here
is a picture of Gert Normann with the
and an assistant off Fort Dansborg. The
local fishermen are very good sailors
were a great help with our investigations.
Measurements with the proton magnetometer in waters
first couple of days we concentrated on scanning the seabed near the old town
of Tranquebar at
Dansborg. All readings were logged as geographical coordinates with the aid of
an occasional sandbank and troughs in the area of the surf, the water became
to the coast the seabed was just sand, though further out there are increasing
amounts of clay sediments.
Gradually the amount of sand decreased leaving just silt.
we registered all the variations and anomalies in an area of 1200 meters along
the coast and
1500 meters out to sea. The research area was then increased. We made a circa
600 metre broad
belt approx. 5 km to the north and approx. 6 km to the south of our initial
It was in this area that there was the greatest probability of
finding wrecks from
ships. The distance from land to the search area was calculated from
measurements of coastal
erosion over the past 200 years.
showed that there were surprisingly few signals registered in the expanded area
what we normally find along the West Coast of Jutland.
1.8 nautical miles north of Tranquebar at position 11 03 287 N and 079 51 931
E, there was
area with signals that was large enough that it could be a small shipwreck.
other signals were found off Tranquebar in a belt from 130 to 380 metres out
from the current
in an area where the dangerous breakers were found in the period from the 17th
that were registered off Tranquebar:
shore by the red outer fort wall outside Dansborg was measured at position 11
01 398 N and
51 380 E.
stairs on the East Side of Fort Dansborg was measured at position 11 01 434 N
and 079 51 371
of the above signals had a size relating to those expected by an iron anchor or
a canon. None of
results were large enough to be interpreted as a whole shipwreck. All
positions are given according to the WGS 84 system.
the ships were anchored for loading and unloading, there were no signals. Therefore
no ship was
sunk at the anchorage off Tranquebar, and only small artefacts or rubbish must
have been thrown
from ships in this area. A lost anchor or canon would undoubtedly have given a
signal on the
can be many layers of debris on the seabed near the anchorage, which are not
registered by the
proton magnetometer. Typical layers of debris at the anchorage include
waterlogged beams, potsherd, bottles, clay pipes and other non-ferrous
section of a chart off Tranquebar Some of the search tracks and all the readings
from the magnetometer are drawn onto the map.
river is misleading, as the subsidiary into the sea is not so broad. The mouth
river is just visible in the southerly turning point of the lines drawn.
The search was
irregular. This was due to the fishing nets and other boats in the water. Subsequently
the gaps in the search area were investigated when there was room.
This resulted in criss-crossing the search area in order to reach the
last areas to be investigated.
would be best to dive and inspect all the positions, which gave a reading and
where locals think there
is something on the seabed. Though due to the rough and murky sea, and the
large amounts of
fishing nets in the area, it was not possible to carry out a safe dive. Most
of the year there are high waves and surf with very murky waters around
talking to a local Indian diver, we learnt that in February and March there was
a good chance for
calm and clear water along the coast. Even though we were in the area in
February, the conditions
were not good enough for us to dive. The best three days the waves were between
1 metre high, and the last two days the waves reached between 1.5 and 2.5
metres high. Every day
the water was murky, even away from the coast. Further out visibility reached a
couple of meters
on the surface, but already at a depth of 2-3 metres the water became totally
thick. During a dive,
Kim Schmidt reached the seabed at a depth of 7 metres in total darkness.
described the water like soup.
comes from the sound of the constant high surf. The local offshore diving boat,
out searches and tried to dive. The boat is equipped with modern diving
equipment and is
crewed by 11 divers and sailors. It is used to supply an offshore drilling rig
south east of Tranquebar.
Investigation of masulas and wooden anchors
fascinating aspect of India is that Old Danish traditions from throughout
history are still present in
life i.e. grinding mills which were used in the Stone Age are still used in
India today. Also boats
built like in the Bronze Age, brickyards from the 17th century, and agriculture
from the 19th century. India also has a modern side with modern machinery,
tools, electronics and
had to days while we waited for our equipment. These were used to investigate a
type of boat, which we wanted to find and measure together with traditional
wooden and stone
masula is a particular type of boat where the planks and frames are bound with
coir in stead of
(exactly as was used in Denmark in the Bronze Age). It was also this type of
boat, which were used
to load and unload frigates at anchorages along the Indian East coast
throughout history. They
also used to load and unload Danish ships.
Gert Normann was in Tranquebar In 1995 he saw a masula, maybe the last original
masula on the
coast. A year later he wanted to document and measure the boat, but the locals
said that the
has been totally destroyed by the waves and there was nothing left.
Knudsen informed us of reports of a masula in a village south of the river in
with Bent Christiansen, we visited the place and found the masula inland, close
for the victims of the tsunami. Unfortunately it was not an old masula, but a
newer version with iron staples instead of the coir binding. Also
the planks were not as broad as in the old masulas,
the size and form were nearly the same. The masula was therefore measured,
videoed and photographed
(see appendix IV).
the current fishing town of Tranquebar we found various wooden and stone
anchors which were measured
and photographed (see appendix IV).
For a literature list on Indian boats see appendix IV.
analysing the readings from the magnetometer in the area off Tranquebar, we
could not find
of a shipwreck in the search area, not even something that would have the size
of a piece of wreckage
floor from the ships broken up in the area.
the anchorage there was found layers with debris and objects fallen from ships,
mostly kitchen waste,
potsherd, clay pipes and small objects, though there was not found metal
objects of a size
were registered by the proton magnetometer. We
got a series of readings in a belt from 130 to 380 metres from the current
coastline, though none
these readings had a size that indicated a large shipwreck. The signals were of
a size corresponding
to a single piece of iron, the size of an anchor or canon, or pieces of a cargo
iron. It could be something that was lost when a smaller boat capsized or sunk.
of a masula can not be measured as these were built of wood and sewed with
coir, so were
to the coastline of Trellund’s map from 1733 we can see that the belt with
to the surf zone in the 17th and 18th century. It was here that small transport
masulas were most at risk of capsize, sinking or being wrecked.
is interesting that we only got readings in this belt off the old town of
Tranquebar and not in the kilometres
long passages north and south of the town, which pass through several fishing
indicates that the signals recorded are probably due to objects lost in
conjunction with activities off
Tranquebar in colonial times.
expected to get readings from pieces of ships that according to history were
broken up off
though the powerful waves that come up the coast may have swept the pieces of wreckage
up on dry land as they became dislodged and free of their cargoes.
positions located by the photon magnetometer need to be investigated by a diver
allow. The greatest chance for calm water and visibility is in February and
March, though it
cannot be taken for granted, so there needs to be a long time period set aside
in these two
in order to guarantee good diving conditions.
can not be expected that a diver, even under good conditions, can find a wreck
or objects from the
17th or 18th century lying on the seabed. All the wooden parts exposed to the
have been quickly decomposed by woodworm and other plant consuming organisms
at them. Only parts of the wreck that are buried in the oxygen free layer under
be well preserved. Heavy items such as iron and other metals that are non-
perishable will quickly
sink into the seabed due to currents and wave movements, and become covered
strength of the proton magnetometer is that it can measure shipwrecks and other
ferrous objects hidden in the seabed.
If there is to be a successful marine archaeological discovery off
Tranquebar, it has to be done
during the best season. The sand and sediment needs to be systematically
removed with a suction pump in a controlled excavation over the investigation area.
18. February 2007
Gert Normann Andersen
preliminary investigation was planned as laid out in this document. (
and deviations are
written in italics.
Plan for the marine archaeological
investigation of the anchorage off Tranquebar
locate ship wrecks or other objects on the seabed off Fort Dansborg in
Tranquebar. This is preliminary
work that could lead to future marine archaeological investigations and
excavations in the
trip and investigation is planned from 2-12 February 2007.
Local working conditions:
conditions in the Tranquebar area are very difficult as there are often large
waves and swells.
Especially the large swells result in strong currents which make working under
water very difficult.
The large swells also swirl the sediment up from the seabed causing reduced
visibility. The best
time for working near the coast is in the winter months from January to March
when the climate is
dry and there is less wind.
Local working conditions:
After interviewing local divers it was confirmed that the best weather and diving conditions are in the
months from January to March. During January the waters often have poor visibility, whereas
visibility is best in February and March.
Unfortunately the water was unclear
during the whole time we were in the area. During the first two days, the waves and surf were about
1 metre high, and during the last 2 days there were a significant number of waves about
1.5 metres and a maximum wave height of 2.5 metres.
Despite these difficulties, we
managed to work every day, apart from one where it was impossible to use the computer and equipment from
the open fishing boat due to spray and flooding. The day was instead used to document wooden
anchors in the village, and preparing our diving equipment for the following day.
A Brief Description of the Assignment:
An initial assessment in Denmark of the objects likely to be found on the
seabed near Tranquebar.
Local fishermen were asked about wrecks or other obstacles on the seabed in the
there for example places where their nets get stuck on the seabed?
A systematic investigation of anomalies at depths of 4-10 metres taken with a
from a local fishing boat.
A systematic investigation of anomalies at depths of 10-15 metres taken with a
from a larger vessel.
A diving survey of potential positions based on information from local
fishermen and anomalies
located by the proton magnetometer.
Although dives were planned
they had to be
abandoned because of low visibility on the seabed, and due to the heights of
which were more than 100% greater than diving permitted.
Discoveries, if found, measured, and documented with underwater video.
7. All results collected into an electronic rapport
with photographs and underwater video.
Use of local vessels:
ship – one day Open
fishing boat three days
Equipment brought from Denmark:
complete with computer, echo sounder and proton magnetometer
camera in waterproof case
sets of flippers
x 15l bottles with harnesses
adapter for an air tank to the regulator/aqualung
aqualungs with mouth pieces
air compressor set (in case we were unable to refill the bottles locally)
tape measure, underwater paper and pencil
Normann –diver and consultant in the area of historical ships
Schmidt – diver and technician Local
helpers where necessary
3/2: Travel: Billund-Frankfurt-Chennai.
4/2: Met with Captain Ramon in Chennai and drove to Tranquebar.
5/2: Visited the site at Tranquebar and interviewed local fishermen.
6/2: Visited harbours and ships. Investigated and measured old transport boats
7/2: Sailed with a small fishing boat and took measurements with the proton magnetometer.
8/2: Continued work from previous day.
9/2: Diving and investigations. (
Due to weather conditions and high
water we tried to work
later in the day. The boat came through the surf, but there was so much water
over the gunnel that we were unable to unpack our equipment from their waterproof
boxes. Instead we sailed back to shore and researched and measured wooden
10/2: Sailed with a large boat with divers and proton magnetometer.
waves were very
high, though we could work with the proton magnetometer because we worked
from a larger vessel than we had on the previous days.
11/2: Packed equipment and drove to Chennai.
Monday 12/2: Return trip Chennai-Frankfurt-Billund
Ships from the Danish East India Company
that have been lost on their journey to and from Tranquebar and East India
Places where ships that were
lost along the Coromandel coast are written in
Places where there is a
chance of finding parts of the shipwreck near Tranquebar are written in
Places where ships were lost
in Northern Europe are written in
RA stands for Rigsarkivet
(The Danish Public Records Office) and the number relates to the archive
registration given in “Vejledende
Arkivregistraturer XIV for Asiatiske, Vestindiske og Guineiske handelskompagnier”.
beached at Tricomale
Christiana beached at Ceylon
Jupiter beached in Bengal
Nattergalen lost in the Bay of Bengal
Flensborg exploded after fight at Cape of Good Hope
scrapped in India
scrapped in India
St. Jacob lost at Pipely in the Bay of Bengal
Solen (Den gyldne sol)
beached on the Dunes, South
on return trip
lost at Petapoli
(Nizampatnam) in May
Den Forgyldte Sol lost on return voyage off South East England
Den Bengalske Prise grounded and totally wrecked at Emeldy, Colconda
Fregatta taken over and lost the same year at Emeldy (north of Madras)
damaged and un-seaworthy in Tranquebar
lost near Gothenburg (RA 191 I)
lost at Læsø
lost at Anholt
beached and destroyed in the Faroe Isles
Havmanden lost (RA192 II)
Den Flyvende Ulv
lost at Plymouth, England on return voyage
Charlotte disappeared in India
along the south coast of India on way to Tranquebar
lost at Læsø (RA194 IV)
Christian Quintus lost in Bengal
Prins Christien lost at Atchin, Indonesia
Prins Carl beached at Bombay
beached and destroyed in the Faroe Isles
lost at Råbjerg Strand, Northern Jutland
Cronprintzen crashed and wrecked (RA194 IV)
beached at Læsø
Den Gyldne Løve
lost on outward voyage from the north coast of
lost on outward voyage off Skagen, North
lost on outward voyage at Fetlar, Shetland Isles
a ship noted as lost
Princesse Lovisa lost on voyage to India off the Maldives (RA665)
disappeared off the
Coromandel Coast on its homeward
three ships noted as lost
lost at Store Dimon, the Faroe Isles, on homeward
Elephanten lost on way from Tranquebar at the Cape (RA 669B + RA 771)
Dokken disappeared on voyage from Tranquebar to København
lost on outbound voyage off Gothenburg
Cron Princessen lost on way to Tranquebar at the Cape (RA670 + RA 773A)
1753 Kongen af Danmark lost on
1763 Grev Moltke
at Negapatnam (RA871b
Haabet lost 12. February
beached along the Swedish coast in the Kattegat
1780 Prs Sophie Friederikke burnt in
1783 Nicobar lost at the Cape (RA208c)
all 47 named ships were lost in the period up to 1772, and four unidentified.
than 40 % (17 out of 47) of the named ships were lost in North European waters
between 1622 and 1783.
ships were lost along the Swedish coast in the Kattegat, off Anholt, Læsø,
Gothenburg, Skagen, the Faroe
Isles, Shetland Isles, Ireland and England.
July 1706, the Evangelical-Lutheran mission lost a chest of money while
unloading to a smaller ship in the sea
Tranquebar. There are also rumours that a number of canons have been lost while
unloading to landing boats.
the period from 1772 to 1791, 159 ships set sail. Of these 137 returned while
22 remained abroad or were lost
Ships from the Dutch East India Company
that are known to be lost off the coast of South East India
8000 voyages to India, about 650 Dutch ships were lost. Many were lost in
Indian waters, though below are only
mentioned those that were lost specifically around the Coromandel Coast.
Eendracht destroyed by fire along the Coromandel Coast
Kleine Davis destroyed by fire along the Coromandel Coast on 11. February
Neptunus beached and lost along the Coromandel Coast on 3. October
Overschie lost along the Coromandel Coast on 21. December
lost along the Coromandel Coast in January
Haarlem destroyed by the French off Pondicherry (became a wreck)
Oostkapelle lost along the Coromandel Coast
Patriot lost off Madurai in South India
Ships from the British East India Company,
that were lost with large fortunes off the coast of South East India
was a part of the British Empire, and as such England had by far the largest
trade with India, and ships.
are only a small proportion of the ships that were lost off South East India.
have material about all the
losses (see literature list), but it is very time consuming to find information
about all these ships.
Eagle lost at Madras, Patnam Roads, with a cargo of coins
Unity lost at Madras on outward voyage with gold
John lost on outward voyage with a cargo of coins, 13.55N 80.14E
Adventure lost on outward voyage with a cargo of coins off Madras - 7. December
Borneo Merchant lost on homeward voyage off Fort St. George, Madras, with gems
- 4. October
Royal Adventure lost south of Mucquav with gifts from the King of Siam, fine
china and gold
outward voyage off Tranquebar with a cargo of coins
King George lost on homeward voyage, from Bengal, off Fort St. George with gems
Dartmouth lost off Madras med 20 cases of silver on homeward voyage, from
- 14. November
beached and lost with
28 chests of coins 85 km north of Tranquebar
Marquis of Rockingham lost near Madras with 23 valuable chests, 22 rescued, -
Earl of Hertford beached and lost off Madras med fine china from China on its
voyage 15. October
Duke of Atholl blown up off Madras on outward voyage with a cargo of coins -
HMS Dover 990 tons, beached and lost off Fort St. George 2. May
Chichester 777 tons Royal Navy Ship beached and lost off Madras - 2. May
Brig Emeraco 101 tons, beached at Covelong (Madras) on voyage to Negapatam -
229 tons, sunk off Negapatam in ballast 9.
a bark lost 100 yards south of River Negapatam - 2.
brig lost at Negapatam - 16.
three ships lost at
Negapatam - two brigs and a dhow
were also an unknown number of other ships and vessels from other periods and
ships from France, Spain,
Portugal and other countries.
are sure that the money chest, belonging to the mission, can be found in the
sea at Tranquebar.
was lost in 1708 while being transferred to a smaller boat.
is also expected to find pieces of ships that were broken up off Tranquebar. Other
ships were lost
at various locations both north and
south of the town.
is a possibility of finding parts of the English frigate Madras which was lost
in 1688 on its outward voyage at
Tranquebar, with a cargo of coins.
is also a possibility of finding parts of the masulas which were used to
transport goods from the ships to shore.
Some of them over the years must have sunk while ferrying goods.
Literature on East India, Tranquebar and
Danish ships in general
Brøndsted, Johannes et al:
Vore gamle tropekolonier
(Volume I, Dansk Ostindien København
Dagbog fra en Ostindiefart 1
(Handels- og Søfartsmuseetpå Kronborg1953)
(GAD, København 1988)
(Wormaniun, Højbjerg 1987)
Krøniker fra Tranquebar
Tranquebar Reconnaissance Report for February 13 – 19.
(Syddansk Universitet 2005)
Rasch, Aa and Sveistrup, P.P.:
Asiatisk Kompani i den florissante
Nogle oplysninger om det tidlige ”Dansk
for Søvæsen 1898, pp. 369-
Literature on shipwrecks including ships
that were lost along the Indian East
Wreck Registers - and Abstract of the Returns to the Board of Trade – Wreck,
Casualties, and Collisions
abroad from 1850 to 1915. Ordered by the House of Commerce and the Board of
Trade. Issued annually
Shipwrecks of the Revolutionary & Napoleonic Eras
(Chatham Publishing, England 1997)
British Warship Losses in the Age of Sail 1650-1859
Sussex, England 1994)
List 1741-1826. Reprinted in 43 volumes
The Atlas of
Shipwreck & Treasure
Web sites and CD
Website over all Dutch VOC Shipwrecks:
Northern Shipwrecks Database Version 2002.
100.000 Shipwrecks World Wide
WRECK LOCATION WITH THE AQUA SCAN MC5
Marine magnetometers have been used in
professional applications with great
success for many years.However the high
cost of these units have restricted
their use for general wreck
location.Recent advances in electronic
technology have however enabled much
cheaper magnetometers to be produced
without sacrificing any of the features
of these professional models.In
fact the use of microcomputers has
enabled costly features on previous
designs to be implimented quite
For wreck location sounder, is its
enable the search buried in sand
difficult with an
the magnetometers great advantage over
an echo ability to detect a wreck at
a distance and then vessel to home onto
it.lt can also detect wrecks etc,
or lying on rocky ground;both of which
are very echo sounder.
The AQUAS CAN MCS is a proton
magnetometer which is used to measure the
earth's magnetic field strength and can
detect variations in this field
caused by the presence of ferrous
objects.The earth's field is normally
uniform, but will be disturbed by local
concentrations of magnetic material
such as a steel wreck.These variations
can extend up to several hundred
metres from a wreck site with the maximum
occurring over the wreck
itself.It is however, difficult to give
accurate performance figures for
the detection of various objects as
much depends on the size,attitude and
permability of the object disturbing
A major feature of the MCS is simple
operation.This has been achieved ,-
by using a
microcomputer to control the operation of the magnetometer.
PRINCIPLE OF OPERATION
The principle of operation of a proton
magnetometer is unlike that of
conventional hand held metal
detectors.These detectors produce their own
dynamic magnetic field and detect
disturbances in the field caused by
metal objects.This time varying
magnetic field only extends about 2 metres
from the search coil,so consequently
the maximum detection range for large
metal objects is still only about 2 metres.Their
main advantage over a
proton magnetometer is that by
generating a time varying magnetic field
non ferrous metals can be detected.The
physical principles on which these
detectors work is outside the scope of
A proton magnetometer for wreck
location measures the strength of the
earth's magnetic field and for this it
is extremly sensitive.The earth's
field is a static field and because
many non ferrous metals do not effect
a static magnetic field then they
cannot be detected by a proton
magnetometer.A good rule of thumb to
determine if a material will be
detected by a magnetometer is if it is
attracted to a bar magnet the it
can be dete~ted.Thc proton precession
magnetometer is so named because it
utilises the procession of spinning
protons in a sample of hydrocarbon
fluid to measure the strength of any
magnetic field through the fluid.In
practice the sensor consists of a
bottle of hydrocarbon fluid
(i.e.kerosene) around which is wound a
coil of wire.
To measure the earth's field, the fluid
must first be polarised for a few
seconds.The polarise state consists of
connecting the coil to a battery
which produces a strong magnetic field
through the fluid. The protons
behave as small spinning magnets and temporarily
align themselves with
this strong field,as shown in (FIG
l).When the battery
is disconnected the magnetic field
collapses and the spin of the protons
causes them to precess about the
direction of the earth's magnetic field.
The precessing protons generate a small
signal of approximately one
microvolt in the coil, and the
frequency of this signal is directly
proportional to the strength of the
earth's magnetic field. The precise
relationship between the frequency of
the signal and the magnetic field
strength is known as the gyromagnetic
Measurements of a masula and anchors
and measurements will be included in the next update.
Literature on Indian boats
The Origins and Ethnological Significance of Indian
(Memoirs of the
Society of Bengal, Calcutta 1920.)
Boote und Schiffe af