The Three Voyages of Captain Cook Round the World. Vol. VII. Being the Third of the Third VoyageKing, James
History
The Three Voyages of Captain Cook Round the World. Vol. VII. Being the Third of the Third Voyage
King, James
Cook, James, 1728-1779 -- Travel; Explorers -- Great Britain -- Biography; Voyages around the world -- History -- 18th century
From this view of the time-keeper it appears, that, for near two years,
it altered its rate very inconsiderably, and therefore, that its error,
according to the Greenwich rate, if we had had no opportunities of
correcting it, would have amounted only to 2-1/4°. That afterward, at
King George’s Sound, or Nootka, it was found to have varied exceedingly;
of course, the longitude, by its Greenwich rate, was becoming
considerably erroneous. About this time, it should be remarked, the
thermometer was varying from 65° to 41°. The greatest alteration we ever
observed in the watch was, during the three weeks we were cruizing to
the north; in which interval, it gave the longitude of the East Cape
with a difference of twenty-eight miles. I have marked the longitude of
Saint Peter and Saint Paul, as given by the time-keeper, notwithstanding
it stopped a few days before we arrived there; this I was enabled to do,
from comparing the longitude it gave the day before it stopped, with
that given by Mr. Bayley’s watch, and allowing for the error of the
latter.
The use of so accurate a measure of time is sufficiently evident, from
its furnishing in itself the means of approximating to the longitude at
sea, as may be seen in the above table. But, besides this, we were
enabled, by the same means, to give a degree of accuracy to the lunar
observations, which they cannot otherwise pretend to; and, at the same
time, by reducing a number of those observations to one time, obtain
results approaching still nearer the truth. In surveying coasts, and
ascertaining the true position of capes and head-lands, it reaches the
utmost degree of practical exactness. On the other hand, it is to be
observed, that lunar observations, in their turn, are absolutely
necessary, in order to reap the greatest possible advantages from the
time-keeper; since, by ascertaining the true longitude of places, they
discover the error of its rate. The original observations, that were
made in the course of this voyage, have been published by order of the
board of longitude; and to those I must refer the reader, for his
further information on this subject.
_N. B._—The observatories were placed on the west side of the village of
Saint Peter and Saint Paul.
Latitude deduced from meridian zenith distances of
the sun, and of five stars to the south, and
five to the north of the zenith 53° 0ʹ 38ʺ north.
Longitude deduced from one hundred and forty-six
sets of lunar observations 158° 43ʹ 16ʺ east.
Longitude by time-keeper, according to its
Greenwich rate 173° 36ʹ 0ʺ
Longitude by time-keeper, according to its rate
found at Owhyhee 159° 20ʹ 0ʺ
Variation of the compass, by azimuths taken with
three compasses, made by Knight, Gregory, and
Martin 6° 18ʹ 40ʺ east.
Public-domain text, read in full here on John Shaqi.
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