' I.'
Ill
4 ,
I . '
i n
I " f I I ,1 i
3 4 6 AP P E N D I X .
magnetic action in consequence of a ship's head being for a considerable
time towards the east, or west : yet this is but a conjecture. In
the measures between Bahia and Rio de Janeiro, and in those between
Rio de Janeiro and Cape Horn, there is no evidence of any permanent
cause of error; but the greater part of those measurements were
made with the ship's head usually near the meridian.
Were I to select three measurements wHch I thought less trustworthy
than others—I should decide on that from the Galapagos to
Otaheite, from Otaheite to New Zealand, and firom Hobart Town to
King George Sound ; but I do not think that either one of these can
be five seconds of time in error, according to regular computation,
without supposing some unknown cause of error to exist. If each
of the three were five seconds wrong, and each error lay in the same
direction, still there would only be fifteen seconds out of thirtytwo
accounted for. Such a supposition as this, however, that each
of these three measurements is five seconds, or thereabouts, in error
(referring only to error caused by known means) appears to be extremely
improbable, I would ahnost say impossible.
I t will naturally occur to the reader, that as error, undetected as
to locahty, exists, arbitrary correction must be made in order to
reduce 24h. Om. 33s. to 24h.
Otaheite has been selected as a point at which such a correction
might be made with the least degree of inconvenience : to that place
the longitudes in the accompanying tables are given as measured
westward by Cape Horn, and eastward from Greenwich by the Cape
of Good Hope ; and there, as the two portions of the chain overlap,
a mean has been taken between the resulting longitudes.
I will now recapitulate the principal measurements, and confront
them with various other determinations. Limited space prevents my
quoting many; but I trust that enough will be given to show that
some weight may be attached to at least a proportion of the results
obtained by the Beagle's officers.
•APPENDIX.
B E A G L E ' S CHAIN OF MERIDIAN DISTANCES AND RESULTING
LONGITUDES in the Atlantic Ocean.
1831—1836.
Plymouth to Port Praya*
Port I'l-aya to Fernando de Noronha
Fernando de Noronha to Babia
Port Praya to Babia*
Bahia to Rio de Janeiro
Rio de Janeiro to Monte Video
347
H. M. s. M. M. s.
) 0 16 40,3
1 17 20,0 1 34 00,3
0 35 39,9 a "9 40,2
0 •24 23,6 —
1 00 03,5 2 34 03,8
0 18 31,4 2 62 36,2
0 52 17,6 3 44 62,8
O T H E R DETEEMINATIONS.
Plymouth (or tbe Government House at Devonport) taken
from the Ordnance Survey and Dr. Tiarks
Captain W. F. W. Owen placed Port Praya in
Dr. Tiarks's longitude of Madeira and Capt. P. P. King's
meridian distance thence to tlie same spot in Port Pmya
placed it in . ...
i6
34
34
17
17
41,4
04,8
02,9
20.7
19.4
03.0
04.1
3 ' , 6
3",4
31.5
19,0
17.8
17,4
18,0
Beagle—Plymouth to Port Praya
Beagle—Port Praya to Plymouth
Beagle—Port Praya to Bahia ...
Beagle—Babia to Port Praya ...
Beagle—Bahia to Rio de Janeb-o
Beagle—Rio de Janeiro to Bahia
Beagle—Bahia to Rio de Janeiro
Captain Foster—Rio de Janeiro to Monte Video
Captam King—Rio de Janeiro to Monte Video
M. Barral—Rio de Janeiro to Monte Video ...
Beagle in 1830—Monte Video to Rio de Janeiro
The longitude of Rio de Janeiro given in this table is very near the latest
determinations of the French, and almost identical with that which is stated,
in the Epbemerides of Coimbra, to have been deduced from upwards of three
thousand observations.
¿Vbifi.—When more than one measurement is stated between the same two
places, it is to be «nderstood that the observations were taken at, or have been
reduced to the same points.
.. • Using the mean of the measureineuts, outward and homeward.