The succeeding morning, the 15th, being then in latitude 63 deg. 33' S., the
longitude was observed by the following persons, viz.
Myself, being the mean of six distances of
the sun and moon 40 deg. 1' 45" E.
Mr Wales, ditto 39 29 45
Ditto, ditto 39 56 45
Lieutenant Clerke, ditto 39 38 0
Mr Gilbert, ditto 39 48 45
Mr Smith, ditto 39 18 15
- - - - -
Mean 39 42 12
Mr Kendal's watch made 38 41 30
which is nearly the same difference as the day before. But Mr Wales and I
took each of us six distances of the sun and moon, with the telescopes
fixed to our sextants, which brought out the longitude nearly the same as
the watch.
The results were as follows: - By Mr Wales, 38 deg. 35' 30", and by me, 38 deg. 36'
45".
It is impossible for me to say whether these or the former are the nearest
to the truth; nor can I assign any probable reason for so great a
disagreement. We certainly can observe with greater accuracy through the
telescope, than with the common sight, when the ship is sufficiently
steady. The use of the telescope is found difficult at first, but a little
practice will make it familiar. By the assistance of the watch, we shall be
able to discover the greatest error this method of observing the longitude
at sea is liable to; which at the greatest does not exceed a degree and a
half, and in general will be found to be much less. Such is the improvement
navigation has received by the astronomers and mathematical instrument-
makers of this age; by the former from the valuable tables they have
communicated to the public, under the direction of the Board of Longitude,
and contained in the astronomical ephemeris; and by the latter, from the
great accuracy they observe in making instruments, without which the tables
would, in a great measure, lose their effect. The preceding observations
were made by four different sextants, of different workmen. Mine was by Mr
Bird; one of Mr Wales's by Mr Dollond; the other and Mr Clerke's by Mr
Ramsden; as also Mr Gilbert's and Smith's, who observed with the same
instrument.
Five tolerably fine days had now succeeded one another. This, besides
giving us an opportunity to make the preceding observations, was very
serviceable to us on many other accounts, and came at a very seasonable
time. For, having on board a good quantity of fresh water, or ice, which
was the same thing, the people were enabled to wash and dry their clothes
and linen; a care that can never be enough attended to in all long voyages.
The winds during this time blew in gentle gales, and the weather was mild.
Yet the mercury in the thermometer never rose above 36; and was frequently
as low as the freezing point.
In the afternoon having but little wind, I brought-to under an island of
ice, and sent a boat to take up some.
