Telegraphic Circuits and Atmospheric Cartography: Collection and Dissemination of Weather Data by the US Army Signal Service, June 1871

Authors: Mark Monmonier*, Syracuse University
Topics: Cartography, Climatology and Meteorology, Communication
Keywords: history of cartography, history of meteorology, telecommunications, weather forecasting, data dissemination
Session Type: Paper
Day: 4/6/2019
Start / End Time: 5:00 PM / 6:40 PM
Room: Virginia C, Marriott, Lobby Level
Presentation File: No File Uploaded


Electric telegraphy made the synchronous weather map an operational forecasting tool. In the late 1850s, Joseph Henry, secretary of the Smithsonian Institution and an inventor of the electromagnetic relay, convinced telegraph companies to have station operators arriving for work send Washington a brief report on early-morning weather and wind direction. Although Henry’s data-collection network demonstrated the practicability of operational meteorology based on commercial telegraphy, the Civil War (1861 – 1865) ended the experiment. After the war, Congress gave the franchise to the Army Signal Service, which set about establishing and equipping a network of weather stations staffed by military weather observers and connected mostly by commercial circuits. This paper examines the twenty-five circuits in operation in June 1871, eight months after the system’s start-up. At junction points like Chicag0 and Boston, data were rekeyed from one circuit onto another. Thrice-daily reports supplied the central forecast office with sufficient data to make nationwide predictions, and even though forecasting was tightly controlled, most stations received sufficient data to make and post their own weather maps. Although contracts with Western Union and other companies guaranteed the dedicated use of key parts of the nation’s telegraph network during fixed parts of the day, government-owned lines were needed to reach remote areas in the interior and along thinly settled parts of the coast. A map in an 1884 history of the Signal Service described the government-run Sea-Coast Telegraph, which collected routine information on winds, waves, and tides, and informed nearby life-saving stations about reported shipwrecks.

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