fact are still doubted, I shall beg leave to call upon Mr. Maskelyne and Mr. Green to declare how near they, with Admiral Tyrrel agreed in determining the Longitude by the Sun and Moon in their voyage to Barbadoes; and also whether during that voyage they ever did determine their Longitude by the Moon and stars.—I know they did not, for they found the observation too difficult, and indeed it is only true in theory.[1]
- ↑ And—(he might have added) troublesome enough in practice, for to many Officers it would be insupportably so; as the reader may judge from the statement herewith, which, taking "The British Mariner's Guide" for a fair criterion, but not having the Pamphlet by us, we insert from the Monthly Review; and it may be regarded as a curiosity, for its contrast with the facility found in resorting to the Timekeeper.—'In the method here proposed, four observations are requisite to determine the Longitude. The first is an altitude of the sun, or some bright star, for regulating a watch, by which the other observations are to be made. The second is the distance of the moon's enlightened limb from the sun or star. The third and fourth observations are, the altitudes of the moon and the sun, or the star, from which the moon's distance is observed; to be taken by two observers assisting the person who takes the distance of the moon from the sun, or star, at the very instant, or, at the utmost, within a minute of the time he gives
with an excellent Hadley's quadrant, rectified by Mr. Hadley himself, and in his presence, attempt to take the angular distance of the Moon from Aldebaran, a star of the first magnitude; but with such bad success (some of the observations removing Greenwich from itself almost as far as Paris) that Dr. Halley seemed to be out of hope of obtaining the Longitude by this method.—Pamphlet. [To the Appendix No. 4.]
