The Island Threehills Lies South Four Leagues From The Coast Of Apee, And
S.E. 1/2 S., Distant Seventeen
Leagues from Port Sandwich; to this, and
what hath been already said of it, I shall only add, that W.
By N., five
miles from the west point, is a reef of rocks on which the sea continually
breaks.
Nine leagues, in the direction of south, from Threehills, lies Sandwich
Island. Twohills, the Monument, and Montagu Islands, lie to the east of
this line, and Hinchinbrook to the west, as also two or three small isles
which lie between it and Sandwich Island, to which they are connected by
breakers.
Sandwich Island is twenty-five leagues in circuit; its greatest extent is
ten leagues; and it lies in the direction of N.W. by W. and S.E. by E. The
N.W. coast of this island we only viewed at a distance; therefore our chart
of this part may be faulty so far as it regards the line of the coast, but
no farther. The distance from the south end of Mallicollo to the N.W. end
of Sandwich Island, is twenty-two leagues in the direction of S.S E. 1/2 E.
In the same direction lie Erromango, Tanna, and Annatom. The first is
eighteen leagues from Sandwich Island, and is twenty-four or twenty-five
leagues in circuit. The middle of it lies in the latitude of 18 deg. 54',
longitude 169 deg. 19' E., and it is of a good height, as may be gathered from
the distance we were off when we first saw it.
Tanna lies six leagues from the south side of Erromango, extending S.E. by
S. and N.W. by N., about eight leagues long in that direction, and every
where about three or four leagues broad.
The isle of Immer lies in the direction of N. by E. 1/2 E., four leagues
from Port Resolution in Tanna; and the island of Erronan or Footoona East,
in the same direction, distant eleven leagues. This, which is the most
eastern island of all the Hebrides, did not appear to be above five leagues
in circuit, but is of a considerable height and flat at top. On the N.E.
side is a little peak seemingly disjointed from the isle; but we thought it
was connected by low land. Annatom, which is the southernmost island, is
situated in the latitude of 20 deg. 3', longitude 170 deg. 4', and S. 30 deg. E.,
eleven or twelve leagues from Port Resolution. It is of a good height, with
an hilly surface; and more I must not say of it.[7]
Here follow the lunar observations by Mr Wales, for ascertaining the
longitude of these islands, reduced by the watch to Port Sandwich in
Mallicollo, and Port Resolution in Tanna.
Port Sandwich, ( Mean of 10 sets of ob. before 167 deg. 56' 33" 1/4 ) E.
( 2 ditto, at 168 2 37 1/2 ) long
( 20 ditto, after 167 52 57 )
( - - - - - - - -
( Mean of those means, 167 57 22 3/4
Port Resolution, ( Mean of 20 sets of ob. before 169 37 35 ) E.
( 5 ditto, at 169 48 48 ) long
( 20 ditto, after 169 47 22 1/2 )
( - - - - - - - -
( Mean of these means, 169 44 33
It is necessary to observe, that each set of observations, consisting of
between six and ten observed distances of the sun and moon, or moon and
stars, the whole number amounts to several hundreds; and these have been
reduced by means of the watch to all the islands; so that the longitude of
each is as well ascertained as that of the two ports above-mentioned. As a
proof of this I shall only observe, that the longitude of the two ports, as
pointed out by the watch and by the observations, did not differ two miles.
This also shews what degree of accuracy these observations are capable of,
when multiplied to a considerable number, made with different instruments,
and with the sun and stars, or both sides of the moon. By this last method,
the errors which may be either in the instruments or lunar tables, destroy
one another, and likewise those which may arise from the observer himself;
for some men may observe closer than others. If we consider the number of
observations that may be obtained in the course of a month (if the weather
is favourable,) we shall perhaps find this method of finding the longitude
of places as accurate as most others; at least it is the most easy, and
attended with the least expence to the observer. Every ship that goes to
foreign parts is, or maybe, supplied with a sufficient number of quadrants
at a small expence; I mean good ones, proper for making these observations.
For the difference of the price between a good and a bad one, I apprehend,
can never be an object with an officer. The most expensive article, and
what is in some measure necessary in order to arrive at the utmost
accuracy, is a good watch; but for common use, and where that strict
accuracy is not required, this may be dispensed with. I have observed
before, in this journal, that this method of finding the longitude is not
so difficult but that any man, with proper application, and a little
practice, may soon learn to make these observations as well as the
astronomers themselves. I have seldom known any material difference between
the observations made by Mr Wales, and those made by the officers at the
same time.
In observing the variation of the magnetic needle, we found, as usual, our
compasses differ among themselves, sometimes near 2 deg.; the same compass too,
would sometimes make nearly this difference in the variation on different
days, and even between the morning and evening of the same day, when our
change of situation has been but very little. By the mean of the
observations which I made about Erromango; and the S.E. part of these
islands, the variation of the compass was 10 deg.
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