Navigators of all nationalities are deeply indebted to Lieutenant Matthew Fontaine Maury, U. S. N., for it was his mind that first conceived the idea of exploring the winds and currents of the ocean. Lieutenant Maury was a Virginian by birth, and in 1825 at the age of nineteen, entered the United State Navy as a midshipman on board the frigate _Brandywine_. In 1830 he was appointed sailing master of the sloop of war _Falmouth_, and ordered to the Pacific station. At this time, being anxious to make a rapid passage round Cape Horn, he searched in vain for information relating to the winds and currents. His attention was thus directed to this subject, and it was upon this voyage that he conceived the design of his celebrated Wind and Current Charts. He also began at this time to write papers for the _American Journal of Science_ which attracted much attention, and on his return he published a _Treatise on Navigation_ which was made a text-book for the pupils of the Naval Academy at Annapolis. In 1842 Lieutenant Maury was placed in charge of the Depot of Charts and Instruments at Washington, which afterwards became the National Observatory and Hydrographic Office. Here he devoted his attention to collecting and converting into systematic tables the valuable data contained in the old log-books of the United States warships, which he found stowed away as so much rubbish, and which had narrowly escaped being sold for junk. At the same time he presented a paper to the National Institute, recommending that all merchant ships be provided with charts of sailing directions, “on which should be daily registered all observable facts relating to the winds, currents, and other phenomena of importance and interest, for the foundation of a true theory of the winds.” A general use of these charts would have constituted one of the greatest exploring expeditions ever devised, but for a time it met with much opposition. Lieutenant Maury’s first convert was Captain Jackson of the Baltimore ship _D. C. Wright_, trading to Rio Janeiro, who made rapid voyages with the aid of the Wind and Current Charts furnished by Lieutenant Maury. Soon there were many followers among American sea-captains, who gave their earnest co-operation and received great benefits in return, since all who kept Maury’s Log, as it was called, were entitled to a copy of the Sailing Directions.