Page:A Voyage to Terra Australis Volume 1.djvu/494

268 In addition to the tables of longitude for the south coast of Terra Australis, I subjoin, for the satisfaction of nautical and geographical readers, a table of the rates of the time keepers, to show their deviations and the errors in longitude during the several passages from one fixed point to another; commencing November 1, 1801, at the Cape of Good Hope, and ending May 9, 1802, at Port Jackson. From this table, the corrections for variation of rates and supplemental error, which have been applied to obtain the corrected longitudes by the time keepers, will be more distinctly seen.

In altering their rates between one station and another, the time keepers are supposed to have done it, not suddenly, but gradually and uniformly, by the quantities marked in the column of daily acceleration; which quantities are the results of the variations in the mean rate during the passage, divided by the number of days. The daily acceleration; is not much in any case, yet it makes a material difference in the longitude after some time; and as the application of this difference has always diminished the error found on arriving at any station, it is a satisfactory proof that the accelerated rate is nearer to the true going of the time keepers on the passage, than the rate found at the commencement.

The difference of longitude produced by the acceleration at