On Thursday, October 20, 1698, a three-masted ship, captained by Edmond Halley with orders “to improve the knowledge of the Longitude and variations of the Compasse,” which he was to observe “with all the accuracy you can,” set sail from Deptford, England, on the first leg of the first voyage ever commissioned for strictly scientific purposes. Halley is now best known as an astronomer and for the comet that bears his name. However, his interests ranged over so many specialties that he is better described now by the 17th century title of “natural philosopher.” Among his various areas of study, the study of the earth took a major place, as shown by his many papers on the trade winds, the tides, and especially the magnetic field. This last interest led him to propose to the Royal Society that he make a voyage around the world “to discover what may be learnt … [of] the variations of the Magneticall Needle.” This ambitious undertaking was later scaled down to cover only the Atlantic Ocean, Halley made two voyages from 1698 to 1700, at one point reaching 52°S in his 52-foot vessel. As a tailpiece he made a third voyage in the summer and fall of 1701 to study the tides and tidal currents of the English Channel.