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.

  • Harrison, John, 1693-1776.
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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    within the Limits required by the Ad of tfie 12th of Queen Anne ; I know it cannot be done. Nay I further call upon any fuch Affronomers to declare, whether even in Ob- fervations of the Diftance between the Sun and Moon, two of them obferving together have generally /peaking agreed in this Obser¬ vation within aMinute of a Degree : I know that in general the Difference between the bed Obfervtrs even at Land will be more, and as a farther Proof of this AfTertion, 1 refer the Reader to the Note below And if f In the fifth Volume of M. De LaCaille’s Ephemerides, Page 31, he fays, cs that any Perfon would be in the wrong to fuppofe that the Longi¬ tude at Sea can be determined by the Moon, to a lefs Error than two Degrees, let the Method which is employed be never fo perfedf, let the In- ftruments, of the Sort now in ufe, be never fo ex¬ cellent, and let the Obferver be the moft able and accomplifhed. For if we examine, without preju-* dice, all the Circumftances which enter into the Cal¬ culation and into the Obfervation of a Longitude at Sea, we fhall be eafily convinced, that it would be ridiculous to maintain, that the Sum of the inevita¬ ble Errors fhould not amount to five Minutes of a Degree, that is, to two Degrees and a half of Lon¬ gitude. N’. B. M. de la Caille publifhed this in the Year 17555 and is univerfally allowed to have been an excellent Obferver, and made feveral Voyages by Sea, where he made Trials of this Me¬ thod by the Moon. Dr. Halley and Dr. Bevis (as appeared to the Honourable Houfe of Commons upon an Examina¬ tion of the latter) did, with an excellent Had¬ ley’s Quadrant, redtified by Mr. Hadley him- felf, and in his prefence, attempt to take the an¬ gular Diftance of the Mopn from Aldebaran, a fr Stax