In the evening I found the variation by the
  mean of azimuths taken with Gregory’s
  compass to be 28 deg. 14’ 0”

By the mean of six azimuths by one of Dr
  Knight’s 28 32 0

And by another of Dr Knight’s 28 34 0

Our latitude at this time was 63 deg. 57’, longitude 39 deg. 38-1/2”

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.