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I. A Proposal of a Method for finding the Longitude at Sea within a Degree, or twenty Leagues. By Dr. Edmund Halley, Astr. Reg. Vice-President of the Royal Society. With an Account of the Progress he hath made therein, by a continued Series of accurate Observations of the Moon, taken by himself at the Royal Observatory at Greenwich.

IT is now above twenty Years since I added an Appendix to the second Edition of Mr. Streets Caroline Tables, containing a Set of Observations l had made in the Years 1683 and 1684, for ascertaining the Moon's Motion; and giving a Specimen of what I thought, at that Time, might be the only practicable Method of attaining the Longitude at Sea. What I printed so long ago, is as follows:

"The Advantages of the Art of finding the Longitude at Sea, are too evident to need any Arguments to prove them. And having by my own Experience found the Impracticability of all other Methods proposed for that Purpose, but that derived from a perfect Knowledge of the Moon's Motion; I was ambitious, if possible, to overcome the Ditliculties that attend the Discovery thereof.

“And first, I had found it only needed a little Practice to be able to manage a five or six Foot Telescope, capable of shewing the Appulses or Occultations of the Fix'd Stars by the Moon, on Shipboard, in moderate Weather; especially in the First