At the top of all the pilot charts issued by the Hydrographic Office of the Navy Department are written these words: “Founded upon the researches made and the data collected by Lieutenant M. F. Maury, U. S. Navy”. This is an appropriate memorial to Maury’s most practical contribution to science,—that which has given him the name “Pathfinder of the Seas”. For a long time he had recognized the need for charts showing the winds and currents of the sea at different seasons; and it will be remembered that, when he was sailing master of the _Falmouth_, 1831–1833, he was first made to realize how little of the nautical experience of other sailors could be taken advantage of by one about to set out on a long voyage. On the way down to Rio in this ship he first conceived the idea of a wind and current chart; but he had no opportunity to make practical investigations into the meteorology of the sea until the year 1842, when he was placed in charge of the Depot of Charts and Instruments. He had been in this office but a short time when he set about examining the old log books which had been stored away as so much rubbish by the Navy Department. By the middle of the year 1843, these investigations had proved so illuminating that he was able to write a paper, which was read before the National Institute, on “Blank Charts on Board Public Cruisers”. According to his plan, these charts were to have parallels and meridians showing the latitude and longitude laid down upon them, and the commanders of ships were to be requested to lay off on them the tracks of their vessels every day, and indicate as well the time of the year, the direction of the winds, the force and set of the currents, and all other phenomena having a bearing on the navigation of the seas on which they sailed. Sailing directions, Maury declared in this address, are now not a written branch of navigation but merely a matter of tradition among seamen. As to his contemplated chart, he boldly asserted that short passages are not due to luck and that “this chart proposes nothing less than to _blaze a way_ through the winds of the sea by which the navigator may find the best paths at all seasons”.