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“ S ir ; Admiralty Office, l ltli November 1831.
“ With reference to the order which my Lords Commissioners
of the Admiralty have this day addressed to you, I am
commanded by their lordships to transmit to you a memorandum,
to be shown by you to any senior officer who may fall in
with you, while you are employed on the duties pointed out in
the above order.
“ I am, Sir, &c.
(Signed) “ G e o . E l l io t .”
“ To Commander Fitz-Roy,
‘ Beagle’ surveying vessel, Plymouth.”
“ Admiralty Office, 11th November 1831.
“ Memorandum.
“ My Lords Commissioners of the Admiralty having ordered
Commander Fitz-Roy, of his Majesty’s surveying vessel the
‘ Beagle,’ to make surveys of various parts of the South American
station, it is their lordships’ direction that no senior
officer who may fall in with Commander Fitz-Roy, while he
is employed in the above important duties, do divert him
therefrom, or in any way interfere with him, or take from him,
on any account, any of his instruments or chronometers.
(Signed) “ G eo . E l l io t .”
“ JMemorandum.
“ A considerable difference still exists in the longitude of
Rio de Janeiro, as determined by Captains King, Beechey,
and Foster, on the one hand, and Captain W. F. Owen, Baron
Roussin, and the Portuguese astronomers, on the other; and
as all our meridian distances in South America are measured
from thence, it becomes a matter of importance to decide between
these conflicting authorities. Few vessels will have ever
left this country with a better set of chronometers, both public
and private, than the Beagle; and if her voyage be made in
short stages, in order to detect the changes which take place
in all chronometers during a continuous increase of temperature,
it will probably enable us to reduce that difference within
limits too small to be of much import in our future conclusions.
“ With this view, the run to Rio de Janeiro may be conveniently
divided into four parts :—
“ 1st. Touching at Madeira, the exact position of which
has been admitted by all parties. Having obtained a four days’
rate there, or, if the weather and the exposed anchorage will
not permit, at Teneriffe, the Beagle should, 2dly, proceed with
the least possible delay to Port Praya, in the Cape de Verde
Islands, not only to establish a fresh four days’ rate ; but that
point being the pivot on which all Captain Owen’s longitudes
turn, no pains should be spared in verifying the position he
has assumed for it. From thence, 3dly, she should make the
best of her way across the Line to Fernando Noronha. This
island, indeed, lies somewhat to the westward of her track, and
may retard her progress a little ; yet a series of chronometric
observations there is essential to the object in view, because it
forms the third nearly equal division of the whole run, and
because it was the point of junction of Commander Foster’s
double line of longitudes. I f two or three days’ delay at either
of these two last stations will enable him to obtain satisfactory
occultations, and moon culminating observations, which are
likely to be seen in tliis country, the increased certainty of the
results will well atone for that loss of time. The Commander
will, of course, be careful to adopt, in all those stations, the
precise spot of the former observations, with which his are to
be compared. The Governor of Fernando Noronha was peculiarly
obliging to Commander Foster, and gave up part of his
own house for the pendulum experiments. There vdll be no
occasion now for trespassing so heavily on his kindness ; but
the difference of longitude between that station and Commander
Fitz-Roy’s must he well measured.
“ However desirable it may be that the Beagle should reach
Bio de Janeiro as soon as possible, yet the great importance of
knowing the true position of the Abrolhos Banks, and the
certainty that they extend much further out than the limits
assigned to them by Baron Roussin, will warrant the sacrifice
of a few days, if other circumstances should enable her to
heat down about the meridian of 36“ W. from the latitude of