THE CHARTS OF NAPAKIANG, AND PORT MELVILLE.
[Sidenote: Different names of this island.]
This island is called Loo-choo, and sometimes Doo-choo, by the natives.
In our maps it is variously written, but mostly Lekayo: the Chinese know
it by the name of Low-kow. The spelling used by Mr. Horsburgh in his
directions, Lieou-kieou, or Lieu-chew.
[Sidenote: Geographical limits and general aspect.]
The island lies between 26º 4-3/4' and 26º 52-1/2', north, and between
127º 34' and 128º 18' east, being very nearly sixty miles long in a
north-east direction, and preserving a tolerably uniform breadth of
about ten or twelve miles. The north end is high and bold, with wood on
the top of the hills. The north-east coast is also abrupt, but quite
barren. The south-east side is low, with very little appearance of
cultivation. The south, south-west, and western faces, particularly the
two former, are of moderate height, and present a scene of great
fertility and high cultivation: it is to this quarter that the mass of
population have resorted. The north-west side is generally rugged and
bare.
[Sidenote: Deep bay.]
[Sidenote: Barrow's Bay.]
There are two deep indentures, one on each side of the island; that on
the west has at least one hundred fathoms depth, and appears to have no
coral in it: while the eastern bight is extremely shallow, and is not
only skirted by a broad fringe of coral, but has reefs in the centre;
and these last are very dangerous, for they give no warning either by
breakers or discoloration of the water, or by soundings: and this remark
will apply generally to all the reefs round this island, rendering the
navigation, particularly at night, very dangerous.
[Sidenote: General caution respecting coral reefs.]
[Sidenote: Sugar Loaf or Eegooshcoond.]
The most remarkable headland is the island called by Captain Broughton
the Sugar Loaf, and by the natives Eegooshcoond (tower or castle); it
can be seen distinctly at the distance of twenty-five miles when the eye
is elevated only fifteen feet. It is a high conical mountain, varying
very little in its aspect when viewed from different quarters: as there
is no other peak like it on or near this island, it cannot be mistaken.
The latitude of the peak is 26º 43' north; and I have reason to believe
that this is within one mile of the truth. Its longitude is 127º 44', or
6' east of the observatory at Napakiang, by two chronometers. The base
of the cone and one-third of the way up is covered with houses; and the
whole island has the appearance of a garden. When nearly on the meridian
of the Sugar Loaf its top seems rounded off.
[Sidenote: Two safe anchoring places.]
[Sidenote: Geographical position of Napakiang.]
There are two places where ships can ride in safety, Napakiang Roads
on the south-west, and Port Melville on the north-west side of the
island. The first of these is the one in which his majesty's ships
Alceste and Lyra lay for upwards of a month. By means of a base of 1319
feet on a coral reef, which dried at half ebb, we were enabled to make
the survey which accompanies this notice. The latitude of the
observatory was determined to be 26º 13' 34" north, the mean of three
meridian altitudes of the sun by a sextant of Cary's, and five by a
circle of Troughton's, the extreme difference being 20". The longitude
is 127º 38' east; this was ascertained by measuring the difference of
longitude between the observatory and Lintin Island off Canton river in
a run of six days; on which occasion two chronometers on board the Lyra
gave within one mile the same difference of longitude, viz. 13º 50',
with that shewn by two others on board his majesty's ship Alceste; the
longitude of Lintin being 113º 48' east of Greenwich. The longitude, by
lunar observations, is 127º 37' 28". The plan of Napakiang roads will be
found sufficient without many directions for ships wishing to enter it.
The principal danger lies in the outer reefs, which do not show when the
weather is very fine and there is little swell; on such occasions a boat
ought to go a-head at least a quarter of a mile, and the ship should put
about instantly upon approaching the reefs, which are every where bold.
A ship coming from the westward ought to steer between the north-eastern
of the group of high islands to the south-westward, and a low green
island with extensive reefs to the northward, in latitude 26º 15' north.
On passing which she should haul up east by south, giving Reef Island a
birth of at least a mile.
[Sidenote: Plan of Napakiang.]
[Sidenote: Directions on approaching Napakiang.]
[Sidenote: Reef Island.]
[Illustration]
[Sidenote: Directions for entering Napakiang roads.]
[Illustration: NAPAKIANG ROADS
_on the S.W. Side of the_ GREAT LOO CHOO Island
_Laid down from actual survey by Captain Basil Hall R.N. H.M. Sloop
LYRA_ 1816]
[Sidenote: Capstan Rock.]
[Sidenote: Best anchorage off the mouths of two rivulets.]
[Sidenote: The northern entrance.]
On approaching the main land a conspicuous wooded point will be seen,
having rocks on its summit like the ruins of an abbey; this forms the
south side of the anchorage, and is considerably more to the westward
than the north-east side. The harbour of Napakiang will soon be seen at
the south side of the bay; steer directly in for this, giving Abbey
Point a birth of half a mile, and when directly between the south end of
the outer reefs and Abbey Point haul up east by north. There is a very
remarkable rock on the south-east side of the anchorage resembling the
head of a capstan. It would be safest to anchor when this bears about
south-south-east half a mile at most, in order to avoid a dangerous
coral tongue, which lies north a little easterly from it, three-quarters
of a mile; but as this anchorage is exposed, the ship may proceed
farther in as soon as the exact place of the reef has been ascertained
by boats; and if she proposes staying any time, she may warp into
Barnpool, taking the precaution of placing a boat on each side of the
entrance. There are two rivulets at this place, and probably the best
anchorage is off their mouths, the bottom consisting of the mud brought
down by the stream. There is a well on the eastern side supplied by a
spring, and there are landing places at the entrance of both harbours.
There is a safe passage between the reef, on which the base was
measured, and the outer ones. The Lyra passed through this three times;
and if the object is to go to the northward it ought to be followed,
provided the wind will admit of steering north and two points on each
side of it. The leading mark for going by this passage is Capstan Fort
or Rock, on with a remarkable nose formed by the trees on the highest
distant land; these are on when they bear about south by east half east.
It would certainly not be advisable for a stranger to enter by this
passage, but he may run on coming from the northward along the shore at
the distance of two or three miles till Reef Island bears west, and then
he should look sharply out for the reefs, keeping outside them till near
Abbey Point, then act as before directed. On running down towards
Napakiang from the northward a remarkable bluff table land will be seen
to the southward of Abbey Point. The west face of Abbey Point ought to
be kept just on with the east end of the table land; this will take you
further out than is absolutely necessary; but it is safe; and when Reef
Island is just on with the northern of the group of distant islands you
will be exactly off the north entrance.
[Sidenote: Appearance of land in coming from the northward towards
Napakiang.]
[Sidenote: Not to be attempted by a stranger.]
[Sidenote: Dangerous coral reef about four leagues south-west by west
from Napakiang.]
On coming from the southward the only danger that lies in the way is a
coral reef even with the water's edge; it is of a circular form, and at
low water several rocks shew on it. On every occasion that we passed the
sea broke high upon it; but from what we saw of other similar reefs, it
seems very probable that when the water is smooth it will give no
warning: it is about eight miles west, 15º north of the extreme south
point of the island, and lies in latitude 26º 7' north, and longitude
127º 26' east of Greenwich.
[Sidenote: Port Melville.]
[Sidenote: Directions to approach it, and to anchor previous to entering
the harbour.]
Port Melville is on the north-west side of the island. A ship wishing to
enter it ought to make the Sugar Loaf Peak, and steer between it and the
cluster of islands to the northward, directly for the bottom of the
bight, which lies between the Sugar Loaf and the north end of the
island; here Herbert's Island will be seen close to the shore, run in
towards its western end, anchor when it bears east one-third of a mile,
and the Sugar Loaf west one-quarter north, barely shut in with a low
dark green point of land; here you will have from seventeen to twenty
fathoms.
[Sidenote: Boats should be sent to buoy the channel.]
The entrance of the harbour is narrow, and ought not to be attempted
without previous examination by the boats of a ship wishing to enter it.
With a very little trouble the passage might be buoyed: a large ship
will probably find it expedient to warp in and out.
[Sidenote: Eye-draught of Port Melville.]
The eye-draught, with the directions on it, render much further notice
here superfluous. The harbour is secure, and sufficiently capacious for
a numerous fleet. It extends in a north and south direction for about
two miles, varying in breadth and form in a very remarkable manner; at
the lower or north end there are two basons of a circular form, and have
from nine to fifteen fathoms, soft bottom; these are about one-third of
a mile across. At some places the steep rocks which form the banks
approach within an hundred yards of one another; here the water is
sixteen, eighteen, and twenty fathoms. There are many fine coves, some
with shelving shores, and others steep-to. Every part of the harbour is
secured from the sea, and many parts from all winds: it is well
calculated for the re-equipment of ships, for it is not only secure as
an anchorage, but offers conveniences for landing men and stores, and
also for heaving down or careening a ship.
[Sidenote: Villages of Cooee and of Oonting.]
There are several large villages on the shores of an extensive bay,
communicating with the sea to the north-eastward, at the upper or south
end of the line of harbours, and one called Oonting on the west side of
the lower harbour; there is another of some extent, on the south side of
Herbert's Island, called Cooee.
By permission of Captain Maxwell, I have named this excellent harbour,
Port Melville, in honour of Lord Viscount Melville, First Lord of the
Admiralty.
[Illustration: _Draught_ _of_ PORT MELVILLE _on the N.W. side of_ _GREAT
LOO-CHOO_ Island _by_ _Captain Basil Hall_ _and_ _the_ OFFICERS _of_
_His Majesty's Sloop_ LYRA _11th Octr. 1816._]
From the top of a range of hills which we ascended, rising on the south
side of the upper bay of Port Melville, we could see the south-west
corner of the great western bay, the whole range of Port Melville, and
the coasts adjacent.
[Sidenote: Geographical position of Port Melville.]
The latitude of Herbert's Island, which lies directly off the entrance
of Port Melville, is 26º 42-2/3' north, by meridian altitude of the sun
observed on shore. Its longitude, which is also the longitude of Port
Melville, is 127º 55' east, or 17' east of Napakiang observatory. The
Sugar Loaf bears from the centre of the island, west 4-1/2º north, about
ten miles.
[Sidenote: Coast skirted by coral reefs.]
As the whole part of this coast is skirted by dangerous coral reefs, the
greatest attention should be paid to the lead, and the ship ought to
be put about the instant that the water shoals to eight, seven, or six
fathoms. On running in for the west end of Herbert's Island, on the
morning of the 11th of October, we passed over a coral ledge having nine
fathoms on it. The west point of Herbert's Island bore at this time
south 8º 40' west, distant four or five miles. Before and after passing
this we had from thirty to sixty fathoms; whether it was shoaler than
nine fathoms at any place, was not ascertained, but the circumstance is
deserving of notice, and ought to teach the necessity of constant
vigilance, when near coral reefs.
[Sidenote: Montgomery islands.]
The cluster of islands to the northward of Port Melville lies between
26º 54' and 27º 4-1/2' north, the north end of the northern one being in
longitude 127º 57' east, or 19' east of the observatory. It does not
appear that there is any good anchorage about them; and there are
dangerous reefs off the south and south-western ones.
[Sidenote: Hope Point.]
The north end of the Great Loo-choo lies in 26º 52-1/2' north, and this
is probably within one, or at most two miles of the truth. We observed
in 27º 00' 15" north, at which time the northern extreme bore east 59º
south, nine miles by estimation, an inference which was checked by the
distance run on a direct course afterwards. The longitude is 128º 9'
east, or 31' east of the observatory.
[Sidenote: Sidmouth Point.]
The coast from the north point runs south-east by east, with some minor
deviations, nearly four leagues: great pains were taken to ascertain
this precisely, as the former charts not only place it many miles
further north, but make the coast at this end lie east and west. The
north-east point lies in 26º 47' north, and longitude 128º 18' east, or
40' east of the observatory. The latitude was determined by the meridian
altitude of Sirius and an altitude of Polaris, so near daylight that the
horizon was well defined; but as this point, off which there is a small
island, was some miles north of the ship at the time of observation, the
above latitude may err possibly two miles. It was intended to have
examined two islands which lie to the north-eastward of the north point,
but a strong current in the night carried us so far to leeward, that we
could not effect this object; the situation, therefore, of these two
islands, may perhaps not be accurately laid down in the chart.
[Sidenote: Barrow's Bay.]
The deep indenture about the middle of the east side of the island is
unsafe to enter during the north-east monsoon: as the wind, however, had
westing in it, we sailed up to within three or four miles of the top,
carrying from thirty to twenty fathoms water; but when about to haul in
for the north side, where there appeared to be a bay, we shoaled
suddenly from twenty-four to eight fathoms: the helm was instantly put
down, and when head to wind, we had only five fathoms. While in stays
the water was observed to wash on a rock not a hundred yards to leeward
of us, on which we must infallibly have struck, had we bore up instead
of tacking.
[Sidenote: South-east coast dangerous.]
From the north-east to the south-east point, the coast runs south 40º
west; the shore to the north-east of this deep bight is bold, and seems
clear; that on the south-west side of it presents a formidable barrier
of islands and coral reefs, which break to a great distance: in fine
weather this part of the coast ought to be approached very cautiously.
[Sidenote: South Point.]
[Sidenote: Reef.]
The southern extreme of this island lies in latitude 26º 4' 46" north,
determined with great care by the meridian altitude of the sun on shore;
and in longitude 127º 35' east, or 3' west of the observatory. There is
good anchorage from twenty to thirty fathoms, south a little easterly,
of this point. Between this point and the group of islands to the
westward, there is a dangerous reef, already spoken of; it lies in 26º
7' north, and 127º 26' east; it bears 26' west, 15º north from the south
point of the island, distant eight miles. Immediately round the point on
the west side there is a shallow harbour, formed by coral reefs, but the
entrance is narrow and intricate.
[Sidenote: South-western group.]
We stood over to the largest of the south-west group, on the east side
of which there stands out a conical rock, behind which it was thought
that a harbour might lie, but upon examination, it proved only fit for
boats; it lies in 26º 11' north.
[Sidenote: Reef Island.]
Reef Island lies west by north, about two leagues from Napakiang Roads;
on the north side the reefs stretch a great way, but the south is more
clear.
Between Napakiang and the Sugar Loaf there is no place for ships to lie
in safety; the bay immediately to the north was examined by Mr. Mayne,
master of his Majesty's ship Alceste, when two shallow harbours were
found.
[Sidenote: Tides.]
The flood runs to the northward and eastward, along shore, and the ebb
in an opposite direction. The rise and fall is about nine feet
perpendicular. High water at full and change IX.
[Sidenote: Variation of the compass.]
The variation of the compass, determined with great precision by the
transit azimuth instrument, was 52' westerly.
The longitude of the Lyra's observatory at Napakiang by the mean of
thirty-six lunar observations on both sides of the moon, is 127º 37' 28"
east; by four chronometers, agreeing nearly, 127º 38' 30" east. The
latitude is 26º 13' 39" north.
[Transcriber's Note: Crescent moons are denoted by [((] or [))]; a circle
with a period therein is denoted by [(.)]]
OBSERVATIONS MADE AT NAPAKIANG OBSERVATORY, GREAT LOO-CHOO ISLAND.
Lunars with a Sextant. Lunars with a Sextant.
[(.)] West of [((] *[Greek: a] Arietis, East of [))]
25th September, 1816. 4th October, 1816
[(.)] [((] 127º. 38'. 15" East. * [))] 127º. 31'. 00" East.
35 . 15 37 . 00
36 . 15 43 . 00
34 . 45 52 . 30
33 . 00 54 . 30
36 . 00 38 . 45
30 . 45 52 . 45
28 . 30 50 . 15
32 . 15 50 . 30
31 . 30 127º. 33'. 39" Mean 41 . 45
40 . 30
26th October, 1816. 34 . 15
43 . 15
[(.)] [((] 127 . 38 . 30 39 . 45
39 . 45 ------------
41 . 30 Mean by sextant 127 . 43. 20 * East of [))]
44 . 15
44 . 30 Lunars by Circle.
32 . 15 [(.)] West of [((]
33 . 00
31 . 45 4th October, 1816
31 . 15 [(.)] [((] 127º. 38'. 45"
27 . 30 127º 36'. 16" Mean 32 . 30
------------- -------------
Mean by sextant 127 . 34 . 58
[(.)] W. [((] Mean 127 . 35 . 37 by circle.
Mean by sextant [(.)] west [))] 127º 34'. 58"
* East [((] 127 . 43 . 20
--------------
Mean longitude by sextant [(.)] * [))] 127 . 39 . 9
by circle [(.)] * [((] 127 . 35 . 37
--------------
Mean longitude by 36 lunars 127 . 37 . 28
Longitude by chronometers 127 . 38 . 30 east of Greenwich.
LATITUDE OF NAPAKIANG.
_By Meridian Altitudes of the Sun and Altitudes taken near Noon._
By meridian altitudes observed. By meridian altitudes deduced in the
usual way from sights taken near noon.
1816. 1816.
Sextant. 8th Oct. mean of 3 A.M.} 26º. 13'. 30" circle.
17th Oct. 26º. 13'. 43" and 3 P.M. }
20th Oct. 26 . 13 . 44 20th Oct. A.M.{ 26 . 13 . 46} sext.
{ 26 . 13 . 44}
Circle.
26th Oct. 26 . 13 . 29 20th Oct. P.M.{ 26 . 13 . 58}
{ 26 . 13 . 47} sext.
{ 26 . 13 . 57}
22d mean 2 A.M.& 2 P.M. 26 . 13 . 24} circle.
26th 3 P.M. 26 . 13 . 29}
Latitude by mean of 3 meridian altitudes 26º. 13'. 39" sextant and circle.
mean of 5 altitudes near noon 26 . 13 . 50 sextant.
mean of 3 do. do. 26 . 13 . 28 circle.
------------
Mean latitude 26 . 13 . 39 north.
* * * * *
VARIATION OF THE COMPASS AT NAPAKIANG.
The declination of the magnetic meridian was ascertained with
considerable precision by means of the transit azimuth instrument: the
needle seldom showed the same variation, as it oscillated about ten
minutes, but the mean position of the magnetic meridian was 52' 10" west
of the true. A coral reef was selected for the place of these
observations, in order to avoid the attraction arising from buildings,
or from inequalities in the ground.
* * * * *
_Variation observed on board by Walker's Azimuth Compass._
29th Sept. 1816, P.M. ship's head W. by S. variation by
1st azimuth 0º. 51'. 30" west.
2nd 0 . 53 . 30
3rd 1 . 17 . 30
Amplitude 1 . 15 . 00
30th A.M. 1st azimuth 0 . 55 . 30
2nd 0 . 34 . 15
3d Oct. A.M. ship's head E.N.E. 1st azimuth 0 . 37 . 00
2nd 0 . 48 . 00
-----------
Variation by mean of 7 azimuths and 1 amplitude 0 . 52 . 39 west.
TABLE OF OBSERVATIONS
MADE WITH
DR. WOLLASTON'S DIP SECTOR:
WITH AN ENGRAVING, AND A DESCRIPTION OF THE INSTRUMENT, AND DIRECTIONS
FOR ITS USE.
[Illustration: Wollaston's Dip Sector]
EXPLANATION OF THE DIP SECTOR,
AND
REMARKS ON THE OBSERVATIONS MADE WITH IT IN HIS MAJESTY'S SLOOP LYRA.
In our tables for apparent dip of the visible horizon at different
heights from the sea, as calculated from the known curvature of the
earth, allowance is made for the refraction of the atmosphere, on a
supposition of its being constant, but as it is known to vary, the
tabular dip will often be erroneous, and, consequently, altitudes taken
under different states of the atmosphere, will exhibit different instead
of corresponding results.
It is foreign to the present purpose to shew what the causes are which
have most effect in raising or depressing the apparent horizon. It may
be sufficient to mention, that changes in the relative temperature of
the air and the sea must produce changes in the refraction near the
surface. Dr. Wollaston has published two papers in the Philosophical
Transactions on this subject, in the volumes for 1800 and 1803, and to
these I beg to refer the reader for precise information upon this very
curious subject.
The object which this sector proposes to attain, is the actual
admeasurement of the dip angle; that is, to ascertain how much the
visible horizon is depressed below the horizontal plane passing through
the eye of the observer. The instrument is so contrived as to measure
double the dip angle twice over, so that we obtain four times the
required dip, and one quarter of this angle is what must be applied to
vertical angles, measured from that part of the horizon which has been
observed.
Figure I. is the instrument seen in perspective, and Fig. II. is a plan
of it with the telescope removed. In order to explain its use, let A and
B (Fig. II.) represent the two reflecting glasses at right angles to the
plane of the instrument, and also nearly at right angles to each other.
It is clear that when the plane of the instrument is held vertically, an
eye situated at E, and looking through the unsilvered part of the glass
A at a distant point C, will at the same time see by joint reflection
from both glasses, another distant point D at 180º from C; and D will
appear to correspond with C, if a suitable motion be given to the index
glass B by the tangent screw F.
The instrument may now be supposed to measure the arc CZD. If the points
C and D be each three minutes farther from the zenith than 90º, the
entire angle will then exceed 180º by double that quantity. The relative
position of the glasses then corresponds to 180º 6', and the six minutes
of excess would be shewn on the arc at F if there were no index error.
But, by reason of the index error, the real quantity will not be known
till a similar observation has been made with the instrument in an
opposite direction.
If the instrument be now inverted, so that the unsilvered glass is
uppermost, the arc intended to be measured is CND, or the sum of the
distances of the points C and D from the Nadir instead of the Zenith,
which of course falls short of 180º by as much as the former arc
exceeded that quantity.
The difference of the two arcs is consequently twelve minutes, and if
the index be now moved till the objects C and D appear to correspond,
the amount of this double difference will be shewn by the _change of
position_ of the vernier.
Hence it is evidently unnecessary that the index error should be
previously known, and even preferable that its amount should be such as
to avoid the needless introduction of negative quantities by positions
on different sides of zero.
In the preceding description, it is supposed that the eye is looking
directly through the unsilvered glass at the horizon, and that it also
perceives the opposite horizon after two reflections; but an inspection
of the figure will shew that the observer's head would necessarily
intercept the rays from the horizon behind him. To obviate this, both
the direct and the reflected rays are received in coming from the
unsilvered glass, (and after passing through the field-glass of the
telescope) on a mirror placed at an angle of 45º, which reflects them to
the eye. By this ingenious contrivance, the obstruction is removed, and
the opposite points of the horizon may be both seen at one moment.
In practice, it is most convenient to direct the telescope to the same
part of the horizon in both cases. Thus, if the east and west parts of
the horizon be observed, and that the index glass be uppermost, and
telescope pointing to the west, the observer is on the south side, and
his face must be turned to the north. When the instrument is inverted,
if the observer turn himself round at the same time, so as to face the
south, then the telescope will be pointed as before to the west; but
since the index glass is now undermost, the inferior arc will now be
measured precisely as if his face were to the north, but with the
advantage of the same lights seen in the erect position of the
instrument.
In using this instrument at sea for the first time, considerable
difficulty arises from the constant change in the plane of the
instrument from the perpendicular position, in which it is absolutely
necessary that it should be held, in order to obtain a correct
observation. What at first appears to be a defect, however, is a real
advantage, namely, that whenever it is held in the least degree out of
the vertical plane, the two horizons (that seen direct, and the
reflected one) cross each other, and it is only when the plane is
vertical that the horizons can appear parallel.
The object is to get the two horizons to coincide exactly, and for this
purpose it will often be necessary to have them of different shades.
This is managed, as in the sextant, by means of the screw, which raises
or lowers the telescope. When the telescope is brought nearer to the
plane of the instrument, the reflected horizon becomes dark and
distinct, but when screwed off it becomes fainter, and is not so well
defined. Practice alone can teach the degree of intensity which is most
favourable. In general it is best to have one horizon dark, and the
other light; then bring them very nearly to coincide, and wait till the
ship is steady, at which moment a slight touch of the tangent screw
brings them exactly to cover one another. It will happen, of course,
that when the coincidence is perfect, there is only one horizon to be
seen, and a doubt remains whether all is right, but a slight motion of
the instrument, by making the horizons cross each other, defines them at
once.
It is advisable to take several observations, and the safest way is to
take one first with the index glass uppermost, and then with the
instrument inverted, after which to return to the first, and so on for
two or three times each way.
In the pages which follow, there is given a table containing the result
of all the observations made during this voyage, preceded by several
sets of observations in the fullest detail. From the table it will be
observed how seldom the dip, actually measured, agrees with that
inferred from the mean refraction. Some of these experiments shew very
remarkable differences, and point out the great utility of this
instrument.
The practical navigator, particularly if he has been in hot climates,
will recollect how discordant his observations for latitude always were,
and how few even of the best observers agree in their determination of
the latitude of the same place, simple as the observation is thought to
be. The cause is quite clear; and though it equally affects altitudes
taken for absolute time, the disagreement is less obvious, and it will
often happen that a chronometer going extremely well appears to vary
every day from inaccuracy in the observations. Thus it is, I think,
generally admitted, that it is almost impossible to rate a chronometer
from altitudes observed with the sea horizon. Nor is this difficulty
removed by taking equal altitudes, because the refraction in all
probability will be different at the two observations. With an
artificial horizon, indeed, the changes in refraction are not felt,
because, at a considerable elevation above the horizon, the changes are
very trifling. But it often happens in practice, that the artificial
horizon cannot be used, and we are then reduced to the sea horizon,
where the changes of refraction are always the greatest. In the Yellow
Sea, for instance, we had no opportunity of landing during all the time
that the squadron was at anchor, till the day before we sailed. So that
during nearly a fortnight that the ships were at anchor, the sea horizon
was necessarily used. I need only to refer to the observations taken off
the Pei-ho, viz. from No. 37 to 62, to shew how extremely fallacious the
results must have been.
It is much to be wished that this excellent instrument should be brought
into general use in navigation.
THE FOLLOWING EIGHT OBSERVATIONS ARE SET DOWN IN THE FULLEST DETAIL, IN
ORDER TO SHEW THE METHOD USED IN RECORDING THEM.
No. 31.
YELLOW SEA.
_July 23, 1816._--6 P.M.
Index uppermost. Instrument inverted.
A + 8'. 10" B - 7'. 10"
8 . 05 7 . 10
8 . 00 7 . 10
------ ------
Mean 8 . 05 Mean 7 . 10 B.
Mean + 8 . 05 A.
-------
15 . 15
-------
3 . 49 Dip.
3 . 50 Tabular.
1 Difference.
-------
Height of the eye, 15 feet, 3 inches.
Parts of the horizon observed, WSW. and ENE.
Barometer 29 . 78 inches
Thermometer {Air 82º
{Sea 77º
Latitude 35º north.
Longitude 124º east.
Wind light from south; horizon uncommonly well defined and sharp; sky
clear, and sea perfectly smooth.
No. 40.
OFF THE PEI-HO, YELLOW SEA.
_July 29, 1816._--9 A.M.
Index uppermost. Instrument inverted.
A + 8'. 20" B - 11'. 40"
8 . 45 11 . 35
8 . 30 11 . 50
------ -------
Mean 8 . 32 Mean 11 . 42 B.
Mean + 8 . 32 A.
-------
4) 20 . 14
5 . 3 Dip.
3 . 50 Tabular.
1 . 13 Difference +
-------
Height of the eye, 15 feet, 3 inches.
Parts of the horizon observed, NW. and SE.
The low land just visible in the NW. distant 12 or 14 miles.
Depth of the sea, 18 feet.
Barometer 29 . 60 inches.
Thermometer {Air 81º
{Sea 84º
Latitude 38º. 50' north.
Longitude 118º. 00' east.
There has been little wind this morning, after a very close night.
No. 43.
OFF THE PEI-HO, YELLOW SEA.
_August 6, 1816._--1 P.M.
Index uppermost. Instrument inverted.
A + 7'. 48" B - 11'. 55"
7 . 48 11 . 45
7 . 55 11 . 45
------ -------
Mean 7 . 50 Mean 11 . 48 B.
Mean + 7 . 50 A.
-------
4) 19 . 38
-------
4 . 54 Dip.
3 . 53 Tabular.
1 . 1 Difference +
-------
Height of the eye, 15 feet, 6 inches.
Parts of the horizon observed, SW. by S. and NE. by N.
Depth of the sea, 29 feet.
Barometer - 29 . 64 inches.
Thermometer { Air 83-1/2º
{ Sea 81-1/2º
Latitude - 38º 50' north.
Longitude - 118º 00' east.
Moderate breeze from SE. by S.; rather hazy, but the horizon sharp and
distinct.
No. 50.
OFF THE PEI-HO, YELLOW SEA.
_August 8, 1816._--6.15. A.M.
Index uppermost. Instrument inverted.
A + 10'. 20" B - 12'. 50"
10 . 18 12 . 45
10 . 35 13 . 00
---------- ----------
Mean 10 . 24, 3 Mean 12 . 51.7 B.
Mean + 10 . 24.3 A.
----------
4) 23 . 16
5 . 49 Dip.
3 . 50 Tabular.
1 . 59 Difference +
----------
Height of the eye, 15 feet, 3 inches.
Parts of the horizon observed, NNE. and SSW. clear of the land.
Depth of the sea, 26 feet.
Barometer 29 . 65 inches.
Thermometer { Air 69-1/2º
{ Sea 78º
Wind NNW. moderate.
Latitude - 38º. 50' north.
Longitude - 118º. 00' east.
_Mem._--The top of the fort at the mouth of the river, is just visible at 30
feet from the surface of the water.
No. 53.
OFF THE PEI-HO, YELLOW SEA.
_August 10, 1816._--6.10. A.M.
Index uppermost. Instrument inverted
A + 13'. 55" B - 7'. 30"
13 . 50 7 . 15
13 . 45 7 . 25
------- ---------
Mean 13 . 50 Mean 7 . 23.3 B.
---------
Mean + 13 . 50 A.
---------
4) 21 . 13.3
5 . 18.3 Dip.
2 . 20 Tabular.
2 . 58 Difference +
Height of the eye, 5 feet, 6 inches.
Depth of the water, 5 feet.
Parts of the horizon observed, N. by E. and S. by W. just clear of the land.
Barometer 29 . 69 inches. } On board His Majesty's ship Lyra,
Thermometer { Air 75º } distant three or four miles.
{ Sea 77º }
Wind WNW.
About one mile from the fort of Tung-coo, at the entrance of the Pei-ho
river. _Note._--Instrument readjusted.
No. 58.
OFF THE PEI-HO, YELLOW SEA.
_August 10, 1816._--2 P.M.
Index uppermost. Instrument inverted.
A + 15'. 40" B - 8'. 50"
15 . 30 8 . 50
15 . 35 8 . 50
-------- --------
Mean 15 . 35 Mean 8 . 50 B.
Mean + 15 . 35 A.
4) 24 . 25
6 . 6.3 Dip.
3 . 50 Tabular.
2 . 16 Difference +
Height of the eye, 15 feet, 3 inches.
Parts of the horizon observed, N. by E. and S. by W.
Depth of the sea, 27 feet.
Barometer 29 . 68 inches.
Thermometer } Air 84º
} Sea 83º
Latitude 38º . 50' north.
Longitude 118º . 00' east.
No. 59.
OFF THE PEI-HO, YELLOW SEA.
_August 10, 1816._--2. 15. P.M.
Index uppermost. Instrument inverted
A + 15'. 10" B - 7'. 50"
15 . 10 8 . 10
15 . 10 8 . 05
--------- ---------
Mean 15 . 13.3 Mean 8 . 01.7 B.
Mean + 15 . 13.3 A.
---------
4) 21 . 15
5 . 48.7 Dip.
3 . 50 Tabular.
1 . 59 Difference.
---------
Height of the eye, 15 feet, 3 inches.
Parts of the horizon observed, NW. by N. and SE. by S.
Depth of the water, 27 feet.
Barometer 29 . 68 inches.
Thermometer { Air 84º
{ Sea 83º
Latitude 38º. 50' north.
Longitude 118º. 00' east.
The vessels in all parts of the horizon have an inverted image under
them; this is very considerable, some having about a third of the sail,
others only the hull.
No. 110.
OFF THE CAPE.
_July 28, 1817._--2.30. P.M.
Index uppermost. Instrument inverted.
A + 6'. 35" B - 5'. 00"
6 . 35 4 . 55
6 . 40 5 . 00
-------- ---------
Mean 6 . 36.7 Mean 4 . 58.3 B.
Mean + 6 . 36.7 A.
---------
4) 11 . 35
2 . 53.7 Dip.
3 . 49 Tabular.
55 Difference -
---------
Height of the eye, 15 feet.
Parts of the horizon observed, SE. and NW.
Thermometer { Air 64º
{ Sea 59º
Depth of the sea, 222 feet.
Latitude 34º. 57' south.
Longitude 20º. 15' east.
Cape Lagullus due north, distant 6 or 8 miles.
Calm all day; sky clear, and weather hazy.
On the 29th and 30th of July we were off the Cape, but the weather was
so bad as to prevent any sights being taken.
[Transcriber's Note: The final column of each of the following
tables is transcribed beneath the table.]
--+--------+----+-----------+-----+-------+-------+-----+-------+------+------+
| |Height Dip. |Diff.|Then. |Differ.| | | | |
| | of +-----------+--+--+---+---+---+---+ | | Long.|Sound-|
No. Date. |eye.| Obs. |Tab.|+ |- |Sea|Air| + | - |Baro.| Lat. | East.| ings.|
--+--------+----+------+----+--+--+---+---+---+---+-----+-------+------+------+
|1816. |f. i|' " |' "| "| "| º | º | | | | º ' | º ' | feet |
18|June 16.|15 3|4 35.0|3 50|45| |83 |82-|1/2| |29.86| 5 11 S|106 3 | 60 |
| | | | | | | |1/2| | | | | | |
19|June 16.|15 3|4 33.0|3 50|43| |83-|82 | 1-| |29.86| 5 05 S|106 10| 56 |
| | | | | | |1/2|sh.|1/2| | | | | |
| | | | | | | |{85| | | | | | |
20|June 16.|14 0|3 59 |3 41|18| |84-|{sh|1/2| |29.83| 5 05 S|106 10| 48 |
| | | | | | |1/2|{95| | | | | | |
| | | | | | | |{su| | | | | | |
21|June 16.|14 |4 01 |3 41|20| |83 |81 | 2 | |29.85| 5 05 S|106 10| 57 |
22|June 27.|16 |4 21.0|3 56|25| |84 |82 | 2 | |29.81| 6 49 N|107 49| |
23|June 28.|16 |4 22.2|3 56|26| |84 |82 | 2 | |29.80| 8 00 |108 10| |
24|July 3. |16 |4 08.2|3 56|12| |84-|81 | 3-| |29.77|13 29 |112 59| |
| | | | | | |1/2| |1/2| | | | | |
25|July 6. |16 |3 53 |3 56| | 3|84 |83-|1/4| |29.75|20 00 |114 | |
| | | | | | | |3/4| | | | | | |
27|July 7. |15 3|4 3 |3 50|13| |85 |85 | | |29.79|21 11 |114 | |
28|July 8. |14 6|3 49 |3 45| 4| |84-|82 | 2-| |29.72| | | |
| | | | | | |1/2| |1/2| | | | | |
29|July 16.|15 3|3 27 |3 50| |23|79 |79 | | |29.75|24 37 |118 56| |
30|July 21.|15 3|3 44 |3 50| | 6|77-|76 | 1-| |29.78|34 |124 | 270 |
| | | | | | |1/2| |1/2| | | | | |
31|July 23.|15 3|3 49 |3 50| | 1|77 |82 | |5 |29.78|35 |124 | |
32|July 23.|15 3|3 49 |3 50| | 1|77 |82 | |5 |29.78|35 |124 | |
33|July 23.|15 3|3 44 |3 50| | 6|77 |82 | |5 |29.78|35 |124 | |
35|July 27.|15 3|4 02 |3 50|12| |76 |76 | | |29.70|38 55 |118 50| 72 |
36|July 27.|13 |3 35 |3 33| 2| |76 |76 | | |29.70|38 55 |118 50| 78 |
37|July 28.|15 3|4 21 |3 50|31| |83 |84 | |1 |29.62|38 50 |118 00 20 |
38|July 28.|15 3|4 06 |3 50|16| |83 |84 | |1 |29.62|38 50 |118 00| 20 |
--+--------+----+------+----+--+--+---+---+---+---+-----+-------+------+------+
Remarks.
---+--------------------------------------------------------------------------+
18 |Weather hazy. The low land of Sumatra just visible. The land wind has |
|been blowing gently for about four hours. |
19 |East and west parts of the horizon observed. Coast of Sumatra just |
|visible. Hazy. The land-wind dying away. |
20 |The day has been extremely hot, and almost a calm. The sea-breeze not yet |
|set in, only a few light flaws. |
24 |A fresh breeze from WNW. The sun set in fiery dirty red clouds. Weather |
|squally, with occasional showers of rain. Parts of the horizon observed |
|east and west. |
25 |Weather remarkably fine; sky clear; and a gentle breeze from the south. |
|The sun set about five minutes after these observations were taken. |
|Parts of the horizon observed east and west. |
27 |The forenoon has been extremely hot and oppressive. A rolling swell from |
|the SW. |
28 |Parts of the horizon observed SSW and NNE, the first clear to seaward, |
| the other clear horizon, but the mainland of China behind it, and |
|various islands on each side of the NNE line. |
29 |Very hazy weather: sky fiery. |
30 |Clear weather, with a light breeze from the eastward. Sun set behind a |
|low range of dark clouds: sky in that quarter was unusually red. A long |
|swell from the northward. |
31 |Wind light from south; horizon uncommonly well defined and sharp; sky |
|clear; and the sea perfectly smooth. These sights, and the two following, |
|may be depended on, I think, within ten seconds. |
32 |Circumstances similar to No. 31. |
33 |Parts of the horizon observed were that immediately under the setting |
|sun; viz. W 21º N, and the opposite E 21º S, the sun being about 4º high. |
|Day has been remarkably clear, although the wind has been from the |
|southward, which in these seas is said generally to bring fogs. |
35 |Weather somewhat hazy; wind easterly. |
36 |Wind easterly. |
37 |These sights were taken while at anchor off the mouth of the Pei-ho. The |
|fort of Tung-coo, on the south bank of the river, bearing W 50º N, distant|
|about four or five miles. |
---+--------------------------------------------------------------------------+
--+--------+----+-----------+------+--------+------+-----+------+------+------+
| |Height Dip. |Diff. |Then. |Differ.| | | | |
| | of +-----------+----+-+---+---+---+---+ | | Long.|Sound-|
No. Date. |eye.| Obs. |Tab.| + |-|Sea|Air| + | - |Baro.| Lat.| East.| ings.|
--+--------+----+------+----+----+-+---+---+---+---+-----+------+------+------+
|1816. |f. i|' " |' "|' " |"| º | º | | | | º ' | º ' | feet |
39|July 28.|15 3|3 46 |3 50| |4|82 |83-| | 1-|29.61|38 50 |118 | 23 |
| | | | | | | |1/2| |1/2| | | | |
40|July 29.|15 3|5 3 |3 50|1 13| |84 |81 | 3 | |29.60|38 50 |118 | 18 |
41|July 29.|15 3|4 00.9|3 50| 10| |84 |83 | 1 | |29.58|38.50 |118 | 20 |
42|Aug. 6. |15 3|5 09 |3 50|1 29| |80 |79 | 1 | |29.64|38 50 |118 | 22-|
| | | | | | | | | | | | | | 1/2|
43|Aug. 6. |15 6|4 54 |3 53|1 1| |81-|83-| | 2 |29.64|38 50 |118 | 29 |
| | | | | | |1/2|1/2| | | | | | |
44|Aug. 6. |15 3|4 47 |3 50 57| |81-|83-| | 2 |29.64|38 50 |118 | 29 |
| | | | | | |1/2|1/2| | | | | | |
45|Aug. 6. |15 3|4 59 |3 50|1 9| |81-|83-| | 1-|29.64|38 50 |118 | 29-|
| | | | | | |1/2|1/2| |1/2| | | | 1/2|
46|Aug. 6. | 3 9|2 39 |1 54| 45| |81 |84-| | 3-|29.62|38 50 |118 | 30 |
| | | | | | | |1/2| |1/2| | | | |
47|Aug. 6. | 6 |3 26 |2 25|1 1| |81 |84-| | 3-|29.62|38 50 |118 | 30-|
| | | | | | | |1/2| |1/2| | | | 1/2|
48|Aug. 6. |15 3|4 59.2|3 50|1 9| |82 |80 | 2 | |29.59|38 50 |118 | 30 |
49|Aug. 8. |15 3|5 47 |3 50|1 57| |78 |69-| 8-| |29.65|38 50 |118 | 26 |
| | | | | | | |1/2|1/2| | | | | |
50|Aug. 8. |15 3|5 49 |3 59|1 59| |78 |69-| 8-| |29.65|38 50 |118 | 26 |
| | | | | | | |1/2|1/2| | | | | |
51|Aug. 8. |15 3|5 47 |3 50|1 57| |77-|73 | 4-| |29.66|38 50 |118 | 24 |
| | | | | | |1/2| |1/2| | | | | |
52|Aug. 9. |15 3|4 30.4|3 59| 40| |79-|75 | 4-| |29.72|38 50 |118 | |
| | | | | | |1/2| |1/2| | | | | |
53|Aug.10. | 5 6|5 18.3|2 20|2 58| |77 |75 | 2 | |29.69|38 50 |118 | 5 |
54|Aug.10. | 5 6|4 28.3|2 20|2 8| | | | | | |38 50 |117 55| |
55|Aug.10. | 5 6|4 7 |2 20|1 47| |77 |75 | 2 | |29.69|38 50 |117 55| 12 |
56|Aug.10. | 5 6|3 55 |2 20|1 35| |77 |75 | 2 | |29.69|38 50 |118 | 13 |
--+--------+----+------+----+----+-+---+---+---+---+-----+------+------+------+
Remarks.
--+---------------------------------------------------------------------------+
39|The day has been exceedingly close with little wind. |
40|There has been little wind this morning, after a very close night. |
41|Nearly calm, there being only a very light air from the SE.--Day sultry. |
42|Weather hazy; sky clear overhead; sea remarkably smooth; wind north. |
43|Moderate breeze from SE by S; rather hazy; but the horizon sharp and |
|distinct. And this together with the four following observations, may be |
|taken as very accurate, every circumstance being most favourable. |
45|Parts of the horizon observed E by N and W by S. |
46|Parts of the horizon observed SSE and NNW. Wind SE. |
47|Wind SE. |
48|Parts of the horizon observed E and W. The day, which has been remarkably |
|fine, has resumed towards sunset a wild, stormy aspect. Wind fresh at SE. |
49|Parts of the horizon observed E by S and W by N. This morning unusually |
|clear; so that when the sun's semi-diameter only was above the horizon, |
|it was painful to look at him. The horizon has a rugged appearance. |
50|Parts of the horizon observed NNE and SSW. Wind NNW, moderate. |
51|Weather remarkably clear; horizon still rugged; wind NNW, moderate. |
52|This morning cloudy, and looks rainy but the air seems clear. Parts of the |
|horizon observed NW by W and SE by E. |
53|Parts of the horizon observed N by E and S by W. Instrument readjusted. |
|Wind WNW. |
54|Parts of the horizon observed WSW and ENE. Wind NW. These observations |
|were taken close to the low land, near the mouth of the Pei-ho. The night |
|had been cold, and the morning was still keen; but unfortunately there |
|was no thermometer in the boat; I suppose, however, that the air was |
|about 66º At the time these sights were taken, I observed a vessel bearing |
|N by W, the lower half of whose sail was inverted. |
55|Wind NW. |
56|Wind NW. Parts of the horizon observed NW and SE. During these |
|observations,(53, 54, 55, 56) the vessels near the land had more or less |
|an inverted image under them. |
--+---------------------------------------------------------------------------+
--+--------+----+-----------+------+--------+------+-----+------+------+------+
| |Height Dip. |Diff. |Then. |Differ.| | | | |
| | of +-----------+----+-+---+---+---+---+ | | Long.|Sound-|
No. Date. |eye.| Obs. |Tab.| + |-|Sea|Air| + | - |Baro.| Lat.| East.| ings.|
--+--------+----+------+----+----+-+---+---+---+---+-----+------+------+------+
|1816. |f. i| ' " |' "|' " |"| º | º | | | | º ' | º ' | feet |
57|Aug. 10.|15 3| 5 37 |3 50|1 47| |78 |76-| 1-| |29.70|38 50 |118 | 26 |
| | | | | | | |1/2|1/2| | | | | |
58|Aug. 10.|15 3| 6 6 |3 50|2 16| |83 |84 | | 1 |29.68|38 50 |118 | 27 |
59|Aug. 10.|15 3| 5 49 |3 50|1 59| |83 |84 | | 1 |29.68|38 50 |118 | 27 |
60|Aug. 11.|15 3| 5 3 |3 50|1 13| |79 |76 | 3 | |29.72|38 50 |118 | 26-|
| | | | | | | | | | | | | | 1/2|
61|Aug. 11.|15 3| 5 13 |3 50|1 23| |80 |79 | 1 | |29.73|38 50 |118 | 24 |
62|Aug. 12.|16 | 4 52 |3 56| 56| |80 |79 | 1 | |29.79|38 50 |118 | 24 |
63|Aug. 12.|15 3| 4 35 |3 50| 45| |81 |79-| 1-| |29.77|38 36 |117 56| 29-|
| | | | | | | |1/2|1/2| | | | | 1/2|
64|Aug. 13.|16 | 4 4 |3 56| 8| |79 |78 | 1 | |29.80|38 31 |118 09| 42 |
65|Aug. 13.|16 | 4 6 |3 56| 10| |79 |78 | 1 | |29.80|38 31 |118 09| 42 |
66|Aug. 13.|16 | 4 20 |3 56| 24| |81 |83 | | 2 |29.80|38 21 |118 04| 44 |
67|Aug. 14.|15 3| 4 30 |3 30|1 | |78 |79 | | 1 |29.71|38 30 |118 24| |
68|Aug. 14.|15 3| 4 25 |3 30| 55| |79-|80-| | 1 |29.70|38 30 |118 35| 50 |
| | | | | | |1/2|1/2| | | | | | |
69|Aug. 15.|15 3| 4 39 |3 30|1 9| |80 |79 | 1 | |29.77|38 00 |118 35| 48 |
70|Aug. 15.|15 3| 4 53 |3 30|1 23| |81-|79 | 2-| |29.76|38 00 |118 54| 44 |
| | | | | | |1/2| |1/2| | | | | |
71|Aug. 15.|15 3| 5 4 |3 30|1 34| |82 |79 | 3 | |29.70|37 54 |118 56| 40 |
72|Aug. 16.|15 3| 4 43 |3 30|1 13| |81 |76 | 5 | |29.17|37 38 |118 57| 39 |
73|Aug. 17.|15 3| 4 38 |3 30|1 8| |80 |79-|1/2| |29.73|37 21 |119 28| 30 |
| | | | | | | |1/2| | | | | | |
74|Aug. 17.|14 | 4 29 |3 41| 48| |81-|81 |1/2| |29.75|37 19 |119 44| 33 |
| | | | | | |1/2| | | | | | | |
75|Aug. 17.|15 3| 4 42 |3 30|1 12| |81-|82 | |1/2|29.70|37 21 |119 44| 30 |
| | | | | | |1/2| | | | | | | |
76|Aug. 18.|16 | 4 39 |3 56| 43| |80 |77 | 3 | |29.76|37 29 |119 37| 48 |
77|Aug. 20.|16 | 4 20 |3 56| 24| |77 |72 | 5 | |29.85|37 50 |120 16| |
79|Aug. 21.|15 3| 4 42 |3 50| 52| |77 |71 | 6 | |29.80|37 52 |120 27| |
80|Aug. 21.| 4 | 2 37 |1 58| 39| |77 |79 | | 2 |29.80|37 52 |120 27| 60 |
81|Aug. 21.|15 3| 4 6 |3 50| 18| |77 |76 | 1 | |29.76| | | 60 |
--+--------+----+------+----+----+-+---+---+---+---+-----+------+------+------+
Remarks.
--+---------------------------------------------------------------------------+
57|Weather very clear. Parts of the horizon observed ENE and WSW. |
58|Parts of the horizon observed N by E and S by W. |
59|The vessels in all parts of the horizon have an inverted image under them; |
|this is very considerable, some having about one-third of the sail, others |
|only the hull. |
60|Light wind from SE. Sky cloudy, somewhat hazy; but the horizon sharp and |
|unbroken. |
61|The inversion of the vessels as conspicuous as before. Parts of the |
|horizon observed ESE and WNW. |
62|A light breeze from the SE. Cloudy and close.--N.B. Instrument readjusted. |
63|Part of the horizon observed N and S. |
64|Part of the horizon observed E and W. A moderate breeze from the SW. Clear |
|overhead; hazy in the horizon. |
65|Parts of the horizon observed N and S. |
66|Wind SE. Sky clear, and the horizon sharp. |
67|Light breeze from ESE. Parts observed NE and SW. |
68|Light breeze at ESE. Cloudy, with a haze in the horizon. Parts observed NE |
|and SW. |
69|Parts of the horizon observed E and W. Moderate breeze from ENE. |
|Remarkably clear weather. |
70|Steady moderate breeze at ENE. Very clear. Horizon sharp, and well defined.|
72|Wind at East. Sky cloudy and rather hazy. |
73|Light wind at SW. Hazy weather. |
74|Light breeze from the Northward. Weather hazy. Parts of the horizon |
|observed SE and NW. |
75|Parts of the horizon observed NE by E and SW by W. |
76|Moderate breeze from East. Parts of the horizon observed WNW and ESE. |
77|The wind has been blowing hard for two days from NE; this evening it has |
|lulled, and the weather has cleared off: there remains however a high |
|swell. |
79|Land-wind South. Fine clear morning. |
80|Parts of the horizon observed SW by S and NE by N. |
81|The inversions which were so conspicuous this morning have been entirely |
|removed since the sea breeze set in. In some distant islands there is a |
|slight inversion at the ends, but very trifling. |
--+---------------------------------------------------------------------------+
--+--------+----+-----------+-------+-------+-------+-----+------+------+------+
| |Height Dip. |Diff. |Then. |Differ.| | | | |
| | of +-----------+----+--+---+---+---+---+ | | Long.|Sound-|
No. Date. |eye.| Obs. |Tab.| + | -|Sea|Air| + | - |Baro.| Lat.| East.| ings.|
--+--------+----+------+----+----+--+---+---+---+---+-----+------+------+------+
| 1816. |f. i| ' " |' "|' " | "| º | º | | | | º ' | º ' | feet |
82|Aug. 21.|14 | 3 26 |3 41| |15|76 |75 | 1 | |29.74| | | |
83|Aug. 21.|15 3| 3 29 |3 41| |12|76 |75 | 1 | |29.74| | | |
84|Aug. 22.|16 | 3 52 |3 56| | 4|75 |76 | 1 | |29.80| | | |
85|Sept. 4.|12 | 3 46 |3 25| 21| |81 |83 | | 2 |29.86| 36 10|126 30| 56 |
86|Sept. 4.|12 | 3 42 |3 25| 17| |81 |83 | | 2 |29.86| 36 8|126 35| 56 |
87|Sept. 5.|15 | 3 47 |3 49| | 2|79 |80 | | 1 |29.80| 35 40|126 17| |
88|Sept. 7.|15 3| 3 33 |3 41| | 8|74 |80 | | 6 |29.84| 34 32|126 34| |
89|Sept. 7.|15 3| 3 27 |3 41| |14|74 |80 | | 6 |29.84| 34 32|126 34| |
| 1817. | | | | | | | | | | | | | |
90|Mar. 3. |14 | 3 57 |3 41| 16| |82 |84-| | 2-|29.74| 2 18|102 20| |
| | | | | | | |1/2| |1/2| | | | |
91|Mar. 5. |14 8| 4 49 |3 46| 1 3| |83 |85 | | 2 |29.73| 3 40|100 35| |
92|Mar. 5. |14 8| 4 50 |3 46| 1 4| |83 |85 | | 2 |29.73| | | 165 |
93|Mar. 5. |14 8| 4 53 |3 46| 1 7| | | | | | | | | |
94|Mar. 8. |14 8| 4 33 |3 46| 47| |84 |84 | | |29.86| 5 12|100 14| 120 |
a)| | | | | | | | | | | | | | |
94|Mar. 8. |14 8| 4 58 |3 46|1 12| |84 |82-| 1-| |29.86| | | 120 |
b)| | | | | | | |1/2|1/2| | | | | |
--+--------+----+------+----+----+--+---+---+---+---+-----+------+------+------+
Remarks.
--+----------------------------------------------------------------------------+
82|This and the following were observed towards sunset; they exhibit a |
|considerable degree of refraction above what is usual. The sights on this |
|morning in the same place gave upwards of 1' greater dip. |
83|All other circumstances the same as in No. 82. |
84|Fresh breeze from SE, with a remarkably clear sky. The horizon uncommonly |
|sharp. |
85|Wind moderate from WNW. Clear weather. |
86|All other circumstances the same as in No. 85. Parts of the horizon |
|observed SSW and NNE. |
87|Parts of the horizon observed WNW and ESE. |
88|The morning has been exceedingly hot before the breezes set in from sea at |
|11 A.M. |
89|All other circumstances the same as in No. 89. |
90|After a very hot day. |
91|Parts of the horizon observed ESE and WNW. See further remarks under 93. |
|Instruments readjusted. |
92|Parts of the horizon observed NE and SW. All other circumstances as in No. |
|91. |
93|Parts of the horizon observed SSE and NNW. These three observations (Nos. |
|91, 92, and 93) were made under the most favourable circumstances, and may |
|be considered as shewing the accuracy which the instrument is capable of |
|attaining. The sea was so perfectly smooth, that not the slightest motion |
|could be detected. The horizon at all the parts observed was sharp, and |
|better defined than I recollect to have seen it; and, what is not often the |
|case, the opposite parts were alike in strength of light &c. The day has |
|been hot, but not close, with a light breeze from the Southward. The dip is |
|very great, but the observations were made with such care, that there can |
|be no doubt of their accuracy. |
94|There had been a light breeze from the North in the morning, but for an |
a)|hour before these sights were taken it had been calm. |
94|Nearly the same place as No. 94(a); but the other circumstances were |
b)|changed, as the sea breeze at NW had set in about a quarter of an hour, |
|whereas in the last instance it was calm. The above angles were taken with |
|great care. The horizon sharp. Parts of the horizon observed NW and SE. |
--+----------------------------------------------------------------------------+
---+--------+----+-----------+------+-------+-------+-----+------+------+------+
| |Height Dip. |Diff. | Then. |Differ.| | | | |
| | of +-----------+--+---+---+---+---+---+ | | Long.|Sound-|
No.| Date. |eye.| Obs. |Tab.| +| - |Sea|Air| + | - |Baro.| Lat.| East.| ings.|
---+--------+----+------+----+--+---+---+---+---+---+-----+------+------+------+
| 1817. |f. i|' " |' "| "|' "| º | º | | | | º ' | º ' | feet |
95|Mar. 19.|14 8| 3 51 |3 46| 5| |80 |82 | | 2 |29.84| | | |
96|Mar. 19.|14 8| 3 48 |3 46| 2| |80 |82 | | 2 |29.78|13 30 | 89 30| |
97|Mar. 20.|14 8| 3 48 |3 46| 2| |79-|82 | | 2-|29.83|14 30 | 89 15| |
| | | | | | |1/2| | |1/2| | | | |
98|Mar. 21.|14 8| 3 48 |3 46| 2| |80 |82 | | 2 |29.84|15 00 | 89 00| |
99|Mar. 22.|14 8| 3 39 |3 46| | 7|79 |79-| |1/2|29.84|16 00 | 88 30| |
| | | | | | | |1/2| | | | | | |
100|Mar. 23.|14 8| 3 47 |3 46| 1| |78-|79 | |1/2|29.80|17 00 | 88 00| |
| | | | | | |1/2| | | | | | | |
101|Mar. 24.|14 8| 3 53 |3 46| 7| |78 |80 | | 2 |29.78|17 30 | 88 15| |
| | | | | | | | | | | |South.| | |
102|July 22 |15 | 3 36 |3 49| | 13|71 |72 | | 1 | |34 0 | 26 | 400 |
103|July 24.|15 | 3 16 |3 49| | 33|59 |62 | | 3 | |34 25 | 24 56| 372 |
104|July 25.|15 | 3 36 |3 49| | 13|62 |63 | | 1 | |35 S | 23 45| 462 |
105|July 26.|15 | 3 30 |3 49| | 19|58 |60 | | 2 | |35 S | 23 | 462 |
106|July 26.|15 | 3 30 |3 40| | 19|60 |63 | | 3 | |34 52 | 22 23| 420 |
107|July 27.|15 | 2 55 |3 49| | 54|56 |59 | | 3 | |35 | 21 | 24 |
108|July 27.|15 | 2 47 |3 49| |1 2|56 |59 | | 3 | |35 | 21 | 240 |
109|July 28.|15 | 3 17 |3 19| | 32|58 |64 | | 6 | |34 58 | 20 15| |
110|July 28.|15 | 2 54 |3 49| | 55|59 |64 | | 5 | |34 57 | 20 15| 222 |
---+--------+----+------+----+--+---+---+---+---+---+-----+------+------+------+
Remarks.
---+---------------------------------------------------------------------------+
95|The wind steady and moderate at NE; atmosphere clear; horizon well defined;|
|a long swell from SW. This swell, which was not high, produced an obvious |
|effect on the dip angle, as observed, the two horizons alternately |
|separating and overlapping; this change was however so slight that I have |
|not been able to measure it. |
96|All other circumstances as in Nov. 95. Parts of the horizon observed NE |
|and SW. |
97|During the night there has been a light breeze from the East; at this |
|moment it is freshening up a little. The atmosphere is clear; horizon |
|sharp; a long low swell from SW, as yesterday. |
98|It has been calm, or nearly so, during the night; occasionally a light air |
|from SE and S. All circumstances favorable. |
99|During the night there has been a light wind from SW. The weather is more |
|hazy than when the wind was from the Eastward, and the horizon not so |
|distinctly marked; but the above sights are good. There is still a swell |
|from SW, which causes some little uncertainty as to the exact moment of |
|taking the angle. |
100|In the night there has been a light breeze from W by S. Weather hazy; but |
|the horizon sharper than yesterday morning. |
101|During the night almost calm; just now a light air from the NE. Parts of |
|the horizon observed NE and SW. |
102|Fine fair clear weather, but with so high a swell as to render the |
|observation difficult. Wind light from N, after having been blowing fresh. |
103|Light breezes from the North-eastward; smooth water, and a clear cool air; |
|hazy about the land. The distance from the South cost of Africa was about |
|8 or 9 leagues. All circumstances seem favourable. No current; we have |
|probably been too near shore for it. |
104|Light breeze from the SW, with a long swell. Hazy weather. The wind has |
|been from the West for 24 hours; at first blowing hard, but latterly |
|moderate, the current setting us to the SW about a mile an hour. A very |
|heavy dew falling this evening. Parts of the horizon observed East and |
|West. |
105|Moderate breeze from the NE; air hazy; long high swell from the Westward. |
|From observations by stars and chronometers, it has been ascertained that |
|there is not the least current. Distance from the South coast of Africa |
|about 50 miles. A high range in sight to the Northward. Parts of the |
|horizon observed North and South. |
106|A light breeze from the NE; air hazy; a long swell from the Westward. |
|About 50 miles distant from the land. |
107|The wind has been moderate from the land all night; air hazy; weather raw; |
|a very heavy dew falling all night. The land in sight to the Northward, |
|distant about 40 miles, is inverted from one end to the other. |
108|Parts of the horizon observed NNE and SSW. All other circumstances as in |
|No. 107. |
109|Parts of the horizon observed NE and SW. Cape Lagullas North 2 or 3 |
|leagues. A light breeze from the Eastward. Air hazy. |
110|Parts of the horizon observed SE and NW. Cape Lagullas due North, distant |
|6 or 8 miles. Calm all day; sky clear; and weather hazy. |
| |
|N.B. On the 29th and 30th of July we were off the Cape, but the weather |
|was so bad as to prevent any sights being taken. |
---+---------------------------------------------------------------------------+
METEOROLOGICAL JOURNAL,
FROM JULY TO NOVEMBER 1816, WHILE THE SHIPS WERE IN THE YELLOW AND JAPAN
SEAS.