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The Flinders papersletters and documents about the explorer Matthew Flinders (1774-1814)
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Letter from the Admiralty re magnetic variations (6 of 7). With copy of Captain Hollis' letter (FLI07)

          Admiralty Office, 28 Decr 1813


          I am commanded by my Lords
Commiƒsioners of the Admiralty to send
for your information the inclosed Copy
of a Letter, transmitted by Admiral
Sir Richard Bickerton, from Captain
of His Majesty's Ship Achille
relative to the Magnetic Influence
which appears to affect the Compaƒs
of Ships, owing to the iron Stanchions
which are placed on each side of
the Capstern [sic] to support the Centre
of the Quarter Deck. I am
        Sir     Your very humble Servt
                              Jn Barrow
Captain Flinders

[Captain Hollis' letter]

Copy               Achille Portsmouth 26 Decr 1813


I beg leave to state to you for the information of the Right Hble the
Lords Commrs of the Admly that I have frequently, observed the
the Compaƒses of H M Ships which I have had the honor of Commanding
differ from each other, & very much from the Compaƒs which I always
carry on the Transom in the afterpart of my Cabin, as well as from
the one which I have on the Forepart of the Poop Deck, & the difference
is of course most when the Ship is sailing in an Eastern or Western direction.
    I am aware of what Captn Flinders has written on this subject, but
I am of opinion that the principal cause of this attraction is owing to the
Magnetic Influence in this part of the Ship being conveyed to the
Three Quarter Deck Compaƒses by the Iron Stanchions which in
all Ships are placed on each side the Capstern to support the centre
of the Quarter Deck, it more particularly attracts the foremost of these
Compaƒses, which is the one the Ship is always Steered by when she is
not sailing by the Winds, when these Stanchions are trued up
they become in a manner neutralized, & I suppose only operates
as any other maƒs of Iron, so as to make the Compaƒses unsteady
but not to fix them — I have been led to make these observations
from knowing the Courses I had ordered the Ship to be Steered
& constantly remarking the difference between the Cabin Compaƒs
as well as of that on the Poop, & those by which the Ship was Steering.
    In sailing Westward down the Mediterranean & Eastward on
running for the English Channel the affect of some strong influence on
the Steering Compaƒses is always apparent, it must be always more

or leƒs on these points of sailing, in proportion to the distance that
is run before it is corrected by an observation & it is not an unusual
practice to attribute this error in the Ships run, to Currents or bad Steerage
which, I think is caused by the influence of these Stanchions in their
vertical poƒsition [sic].
    I had always noticed extraordinary attractions of the Compaƒses
without being able to discover the causes until I commanded the Mermaid
on the Nova Scotia Station. I was returning to Halifax in company with
H M S Isis, & was then running between Sable Island & the chain & in
the evening had made the Signals & shaped a course for the Night.
Fortunately the Ships had not run their distance, & in the Morning
by a conversation that took place with the Isis I found the Mermaid
had been steering about one point & a Quarter more to the Northward
than the Isis, this was so extraordinary & so great a difference, that I
was determined if poƒsible to find out the cause — I directed the Isis to
go ahead, & steer (I think) West, I followed close in her Wake, & by my
Binnacle Compaƒses I was Steering about W by N ¼ hs . I then had every
thing that was attractive removed from that part of the Ship & ordered
4 or 5 layers of Blankets, & canvaƒs to be nailed over the Quarter
Deck Hatchways without effect, all the Compaƒses in the Ship
were at this time placed on different parts of the Quarter Deck
& had been alternately shifted into the Binnacle, & the whole of them
pointed the Ships head to be nearly West except those in the Binnacle.
I had been running on this course about two hours when I ordered
the Iron Stanchions to be triced up & the Compaƒses in the
Binnacle immediately veered to the West, I caused this to be
frequently repeated, & found the result the same Viz about
one Point & a Quarter. I think this a Strong proof that

when the Compaƒses are within the Influence of these Stanchions
in their vertical poƒsition [sic], that they must be in some degree
operated upon, & that influence will be in proportion as the N
or South points of the Needle are directed toward the upper ends
of the Stanchions. Bearing these facts in my mind I have at
different times made the same trials in the Standard &
Achille, but they did not produce the same effect, the results
have been about half a Point. Since the first circumstance
occurred I have always had the Stanchions covered with
canvaƒs, & painted it may be partly owing to the distance being
greater from the Compaƒses in a Ship of the Line than a Frigate
or from the lower deck intervening, & a current of Air paƒsing
through the Ports & altering the natural course of the Magnetic
Influence — On my arrival at Halifax I wrote a Public letter
to the Commiƒsrs & the aftermost of these Stanchions was removed
& this a remarkable coincidence that HMS the Pallas had
just arrived at Halifax from England had made a represe-
=tation of the influence of her Compaƒses during the run out, & was having the iron Work shifted from about the Binnacle on that account.
    I hope their Lordships will pardon my having treƒpaƒsed [sic]
so much on their time in presuming to offer my opinion on this
subject & I beg leave to aƒsure them that I am only induced to do so
from a zeal for my profeƒsion, & a wish that it may lead
by the aƒsistance of Scientific Men to the Safer Navigating
of H M Ships. I have &c
                                  (signed) A P Hollis

Adml Sir R Bickerton
Commander in Chief
    &c     &c     &c

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Related people
Bickerton, Sir Richard
Hollis, (Captain) Askew Paffard
Barrow, John
Flinders, Matthew


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