Lectures on select subjects in mechanics, hydrostatics, pneumatics, and optics. With the use of the globes, the art of dialing, and the calculation of the mean times of new and full moons and eclipses / By James Ferguson.

  • Ferguson, James, 1710-1776.
Date:
1760
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on select subjects in mechanics, hydrostatics, pneumatics, and optics. With the use of the globes, the art of dialing, and the calculation of the mean times of new and full moons and eclipses / By James Ferguson. Source: Wellcome Collection.

    446/486 (page 390)
    When the altitude is given, find from thence the hour, and proceed as above. , This praxis is of fingular ufe on many occafions i in finding the declination of vertical planes more exadly than in the common way, efpecially if the trail fits of the fun's center is Gbierved by applying a ruler with fights, either plain or telefcopical, to the wall or plane, whofe declination is required,—» Ib drawing a meridian line, and finding the mag¬ netic variation.finding the bearings of places in terreftrial furveys ; the tranfits of the fun over ' !« any place, or his horizontal diftance from it being obfcrved, together with the altitude and hour.— And thence determining fmall differences of longi¬ tude.— In obferving the variation at fea, &c. The learned Mr. Andrew invented an infiru-* ment feverai years ago, for finding the latitude at fea from two altitudes of the fun, obferved on the fame day, and the interval of the obfervations, meafured by a common watch. And this inftru- ment, whofe only fault was that of its being fome*** ’ what expenfive, was made by Mr. Jackfon* Ta^ blcs have been lately computed for that purpofe. But we may often, from the foregoing rules, re^^ fblve the fame problem without much trouble; ef¬ pecially if we fuppofe the mafter of the fhip to know within 2 or 3 degrees what his latitude is. Thus, Afilime the tv/o neareft probable limits of the latitude, and by the theorem H~ ? compute the hours of obfervation for both fuppofitions. It one mterval of thofe computed hours coincides with