In the year 1714, several captains and owners of merchant vessels petitioned the House of Commons to consider the propriety of bringing in a bill to reward inventions for promoting the discovery of the longitude at sea. A committee was appointed to investigate the subject, and Mr. Ditton and Mr. Whiston, having thought of a new method of finding the longitude, submitted it to the committee. Four members of the Royal Society, viz. Sir Isaac Newton, Dr. Halley, Mr. Cotes, and Dr. Clarke, were examined on the subject, along with Mr. Ditton and Mr. Whiston. The last three of these philosophers stated their opinions verbally. Mr. Cotes considered the proposed scheme as correct in theory and on shore, and both he and Dr. Halley were of opinion that expensive experiments would be requisite. Newton, when called upon for his opinion, read the following memorandum, which deserves to be recorded. “For determining the longitude at sea there have been several projects, true in theory, but difficult to execute. “1. One is by a watch to keep time exactly; but by reason of the motion of the ship, the variation of heat and cold, wet or dry, and the difference of gravity in different latitudes, such a watch hath not yet been made. “2. Another is by the eclipses of Jupiter’s satellites; but by reason of the length of telescopes requisite to observe them, and the motion of a ship at sea, those eclipses cannot yet be there observed. “3. A third is by the place of the moon; but her theory is not yet exact enough for that purpose; it is exact enough to determine the longitude within two or three degrees, but not within a degree.