Page:Philosophical Transactions - Volume 004.djvu/61

 At the Rising and Setting of the Sun, when it is half above the Horison, marke the time of the day, which the Watches, then shew; and though you have in the mean time sayl'd on, it is not considerable. Then reckon by the Watches, what time is elaps'd between them, and add the half thereof to the time of the Rising, and you shall have the time by the Watches, when the Sun. was at South; to which is to be added the Æquation of the present day by the Table. And if this together makes 12. hours, then was the Ship at Noon under the same Meridian, where the Watches were set with the Sun. But if the summe be more than 12, then was she at Noon under a more Westerly Meridian; and if less, then under a more Easterly; and that by as many times 15. degrees, as that Summ exceeds or comes short hours of 12: as the Calculation thereof hath been already deliver'd.

Suppose, e. g. that the Watches A and B, as before, were set with the Sun at the place whence you parted, the 20th of Febr; and the Indexes set to the Hour, min, and second, shewed by the Sun, abating the, Æquation of that day, viz. 2. min. and 20. seconds; the Watch A being reduc'd to the right measure, and B going too slow by 7. sec. a day. Afterwards on the 22th of May, desiring to know the Longitude of the place, to which you are come, you observe in the Morning the Sun Rh