A masterpiece of data visualization, compiled by Matthew Fontaine Maury to depict the Atlantic Trade Winds.

This chart was designed to allow navigators to take advantage of the Northeast and Southeast Trade Winds in the Atlantic Ocean while avoiding the adjacent calms (The Trade Winds are steady easterly winds that originate in the subtropical high-pressure belts over the North and South Atlantic, roughly around 30° latitude, and blow toward the equatorial low-pressure zone.) In all the chart provides data for six distinct wind patterns; from top to bottom, corresponding to north to south, these are:

• “Region of calms above the N.E. Trade Winds” (pink)
• “Region of the N.E. Trade Winds” (blue)
• “Equatorial Calms” (pink)
• “S.W. Monsoons” (dark blue/purple) (“Monsoons”, in Maury’s terminology, occur when northeast and southeast trade winds meet near the Equator, producing calm spells, squalls, and heavy rain.)
• “Region of the S.E. Trade Winds” (blue)
• “Region of calms below the S.E. Trade Winds” (pink)

The design is ingenious, integrating the coordinate grid of a map with elements adapted from statistical tables and run charts. But it’s also fiendishly complicated. I’ll mostly let Maury speak for himself, beginning with an account of the grid that provides the framework for presenting the wind data:

“The horizontal lines are parallels of Latitude. The heavy vertical lines are meridians for every even 5° & 10° of Longitude. The 12 vertical columns between the meridians show the months, commencing always with December the first Winter Month.”

Thus, every “cell” on the grid represents a given month at a given latitude, within a band of 5° longitude. Within many cells are numbers, corresponding to the number of recorded observations at that location. So, for example:

“Let the Ship be in the region of Horse Latitudes between the meridians of 40° and 45W. She will observe that 45 Vessels have in various years, between these two Meridians and in July encountered these calms, Viz. 3 between Latitudes 37 and 38°; 3 between 35° and 36°; 7 between 34 and 35°; 3 between 33° and 34°; 12 between 32° and 33°; 4 between 31 and 32°; and so on to the parallel of 25°, below which none of these calms are found in July and between these Meridians.”

Click here for a detail of the chart highlighting the section in question.

Perhaps even more remarkable than the chart’s design are the sources: Maury and his assistants began with a “deep dive” into U.S. Navy archives, mining the wealth of data in its trove of annotated charts and log books. They greatly augmented this by crowdsourcing information from cooperative navigators, who were compensated for their efforts with complementary sets of Maury’s Wind and Current Charts.

Maury issue a new edition of the chart in 1858. Though this new edition was entirely re-drawn, there are only minor differences of formatting, while the data appears to be identical. The 1851 edition is well represented in institutional collections, but both editions are quite scarce on the market.

Matthew Fontaine Maury
Maury (1806-1873) was born near Fredericksburg to a distinguished Virginia family and numbered among his ancestors the Rev. James Maury, one of Thomas Jefferson’s most influential teachers. When he was five his family removed to Tennessee, where at 19 he received a commission in the U.S. Navy through the influence of Senator Sam Houston. During the early years of his service he developed a strong interest in hydrography, meteorology and navigation. At 33 a stagecoach accident ended his career at sea, but in 1842 he was appointed to superintend the Navy’s Depot of Charts and Instruments, later renamed the United States Naval Observatory, a role he filled with great ability until the outbreak of the Civil War.

At the Observatory he sought the linked goals of extending science and improving navigation, in part through compiling and interpreting the raw data locked in the Navy’s vast collection of annotated charts and log books. More innovative still was his institution of a reporting system whereby shipmasters recorded and communicated to him the sea and weather conditions they encountered. This wealth of data enabled him to begin publishing in 1847 his Wind and Current Charts of the world’s oceans. This series was divided into six groups: Track Charts, Trade-Wind Charts (including the chart offered here), Pilot Charts, Whale Charts, Thermal Charts, and Storm and Rain Charts. These were followed in 1855 by his Physical Geography of the Sea, the first comprehensive book on oceanography in any language.

Like his friend Robert E. Lee Maury was strongly anti-secession, but also like Lee his loyalty to his home state of Virginia superseded that to the Union. After Virginia’s secession Maury resigned his commission and was commissioned first as Commander of the Virginia navy and then as a Commander in the Confederate navy, in charge of its Naval Bureau of Coast, Harbor, and River Defense. In this latter capacity he helped develop an electrically-controlled mine, which throughout the war caused much damage to blockading vessels of the Union Navy. In the Fall of 1862 he was sent to Europe, where he spent the remainder of the war seeking—with little success–to acquire ships and supplies and to encourage European nations to intervene on the side of the Confederacy.

At war’s end he traveled to Mexico, where he participated in a short-lived scheme to encourage former Confederates to emigrate and establish a slaveholding colony. After receiving a pardon from the Federal Government, he returned to Virginia in 1868 and took a professorship at the Virginia Military Institute, a position he held until his death in 1873. During this time he produced the Physical Survey of Virginia and lectured extensively both in the United States and abroad.

Maury did not own slaves, but the historical record demonstrates his support for the institution. As a result he is very much back in the news today: In July 2020 the mayor of Richmond ordered his statue removed from its location, Maury Lake on the grounds of the Mariners’ Museum in Newport News has been renamed, and in 2023 the U.S. Navy renamed the oceanographic survey ship USNS Maury after oceanographer Marie Tharp. His supporters can take comfort in the many historical markers still dedicated to him, as well as Maury Crater on the Moon.

Edwin Jesse DeHaven
DeHaven (1816-1865) was a U. S. naval officer, with a distinguished naval career as an explorer. Early in his career he participated in the United States Exploring Expedition (aka the Wilkes Expedition) of 1839-1842. He went on to command one of the two ships in the First Grinnell Expedition, the American contribution to the search for Sir John Franklin’s missing expedition to the Arctic. After his return from the Arctic, he served first at the United States Coast Survey and then with Maury at the Naval Observatory. In 1862, he was compelled to retire when his eyesight failed.

References
OCLC #666700448 et al, locating numerous institutional holdings. David Rumsey Map Collection, #14494.016. Background on Maury from Charles C. Bates, “Marine Meteorology at the U. S. Navy Hydrographic Office—A Resumé of the Past 125 Years and the Outlook for the Future”, Bulletin of the American Meteorological Society, vol. 37 no. 10 (Dec. 1956), pp. 519-527; and Tim St. Onge, “Scientist of the Seas: The Legacy of Matthew Fontaine Maury”, posted online July 25, 2018 at Worlds Revealed: Geography & Maps at the Library of Congress.