Page:Philosophical Transactions - Volume 004.djvu/62



'Tis manifest, that by this way you find precisely enough the Longitude of the place, where you were at Noon, or the Time of the Suns being in the South: which, although it differs from the Longitude of the place, where you are when you observe the Setting of the Sun, yet you may estimate neer enough, how much you have adyanc'd, or chang'd the Longitude in those few hours, by the Log-line, or other Ordinary practises of reckoning the Ships way; or (which is the surer way) by the degrees pass'd in 24. hours by a former days Observation.

You may also, instead of observing the Suns Rising and Setting, observe the setting first, and then next morning the Rising; marking at both times the Time show'd by the Watches; and find thence, after the same manner as before, the Longitude of the place where the Ship was at Midnight.

Finally, you may also, instead of the Rising and Setting of the Sun, observe before and after Noon two equal Altitudes of the Sun, noting the time shown by the Watches, and reckoning in the same manner, as hath been said of the Rising and Setting: Yet it is to be consider'd that the Altitudes of the Rh