<2<ji« cook's VOYAGE TO OCT. 



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, ac- 

 cording to the Greenwich rate, if we had had 

 no opportunities of correcting it, would have 

 amounted only to 2£°. 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 cruiz- 

 ing 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 suffi- 

 ciently 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 can- 

 not 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 5 since, by ascertaining the true longitude 



