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292 [[circled, top right of page]]

[[left margin]]From Gents Mag. for 1737 Vol. 7. p. 616.[[/left margin]]

[[Underlined]]To find the Longitude at Sea without Instruments.[[/underlined]]

[[left margin]]Fig. 52. [[/left margin]]

One may judge his Longitude within 4 Deg. or the Time at [[underlined]] London [[/underlined]] within 1/4 of an Hour, which will give N the Place of the Moon's Node within 2 Seconds, its mean Motion being but 3 Min. 11 Seconds in 24 Hours, and to find its R. Ascension, and the Hour by it before 6 (i.e.) the Angle EPN; [[which?]], with EP, and the Latitude PER, gives PB or BN, and also PBE or EBN; which two, with PNC, the Angle made by the Moon's Path (which makes about 5 Deg. with Eclip.) and its Meridian then, gives Nn; but the Moon's Vertex at rising is found, by substracting the Refraction from the Parallax, suppose it to be 24 Min. above the Horizon or the Center c, 9 Min. (the 1/2 Diam. being 15); then co being 9 Min. that, with the Angle n, gives cn to be added to nN, and you have the Distance of the Moon's Center then from the Node N, whose Place was before found; and having done so before at the Place departed from, where the Longitude was known, you have the 2 Distances from the Node, and by substracting the one from the other, and the Min. the Node hath moved from the Remainder, you have found the Arch in the Moon's Path thro' which the Moon hath gone since you left the first Place, and beginning at the mean Anomaly answering the Moon's first Place, count up its horary Motions till you make up the Deg. the Moon hath moved, changing its horary Motions till you make up the Deg. the Moon hath moved, changing its horary Motion every 6 Deg. the Tables being only made for each 6 Deg. the Hours and Min. answering these horary Motions being added to the Time at [[underlined]] London [[/underlined]], gives the Hour there. 

Note.