Remarks on a pamphlet [respecting H.'s chronometer] lately published by the Rev. Mr. Maskelyne, under the authority of the Board of Longitude / By John Harrison.

  • John Harrison
Date:
1767
Catalogue details

Licence: Public Domain Mark

Credit: Remarks on a pamphlet [respecting H.'s chronometer] lately published by the Rev. Mr. Maskelyne, under the authority of the Board of Longitude / By John Harrison. Source: Wellcome Collection.

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    The Method of finding the Longitude by the Moon, in which Mr. Maskelyne is in a pecuniary way interefted, is this.—If the apparent Diftance between the Sun and Moon, or between the Moon and fome fix'd Star, at any certain Part of the Globe, was for every Hour of the Year known ; and if a Navigator, when at Sea, could alfo, by Obfervations, afcertain what is the apparent Difiance, at the Place where he is, between the Sun and Moon, or between the Moon and a Star, and likewife their refpective Altitudes; and if he could alfo, at the fame Moment, afcertain the Time of the Day, either by an immediate Obfervation of the Sun, or by a Watch which would keep Time pretty exactly from the laft folar Ob¬ fervation ; thefe Matters of Fact being given, the Difference of Longitude may from thence be calculated. I admit the Principle to be abfolutely true in Theory. The Lunar Tables, for which the Rewards have been given, are calculated to fhew the Difiance between the Sun and Moon, or Moon and Stars, at Greenwich ; I admit the Practicability of making fuch Tables ; but with Regard to the other Requifites, I beg Leave to obferve that, for fix Days in every Month, the Moon is too near the Sun for obferving, confequently, during thofe Days, the Method falls totally to the Ground ; that for about other thirteen Days in every Month, the Sun and Moon are at too great a Difiance for obferving them at the fame Time, or are not at the fame Time vifible ^ therefore, during thofe 13 Days, we muft de¬ pend
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