henry (H)		Joseph Henry (1797–1878)

Joseph Henry was an American physicist, meteorologist and scientific administrator. He is generally considered to be the "father" of the US National Weather Service. He also discovered electromagnetic induction independently of Faraday. As a result of that discovery, Henry's name was given to the SI (International System of Units) unit of inductance. One henry is equal to an electromotive force of one volt in a closed circuit with a uniform rate of change of current of one ampere per second.

Henry developed an interest in meteorology during the time he spent as a professor at Albany Academy in Albany, New York. While there he collected statewide weather observations for the University of the State of New York. Later, he was a professor at the College of New Jersey in Princeton where he conducted research on lightning and studied storm patterns and atmospheric physics.

Henry became first secretary of the newly-formed Smithsonian Institution in 1846. He would serve in that capacity until his death in 1878. He immediately set up a meteorological program at the Institution and in 1847 called for "a system of extended meteorological observations for solving the problem of American storms". He clearly understood that the electric telegraph would play a key part in such a system. Henry had described the basic scientific principles of the telegraph in the early 1830s, but Samuel Morse is credited with the actual development of the telegraph. Henry knew that storms in the US generally moved from west to east (Benjamin Franklin was the first to realize this) and wrote in the Smithsonian's 1847 annual report that "the extended lines of the telegraph will furnish a ready means of warning the more northern and eastern observers to be on the watch for the first appearance of an advancing storm".

By 1849 Henry had established a network of some 150 volunteer weather observers linked by telegraph. He convinced several telegraph companies to transmit weather data to the Smithsonian free of charge. The Institution served as the administrative and scientific centre of the weather telegraphy network. It provided instructions, standardized forms and in some cases instruments to the observers, who were expected to make several observations each day of temperature, barometric pressure, humidity, wind, cloud conditions and precipitation amounts. They were also instructed to note "casual phenomena" such as thunderstorms, hurricanes, tornadoes, earthquakes, meteors and the aurora. All this information was summarized in monthly reports submitted to the Smithsonian, where Henry used it to create a large daily weather map whose purpose was, as he wrote, to "show at one view the meteorological condition of the atmosphere over the whole country". The map was displayed for the first time in 1856 in the Castle (the original building of the Smithsonian Institution). It used a system of colored disks to indicate the type of weather observed (blue for snow, black for rain, brown for cloudy conditions and white for fair weather) with arrows showing the prevailing wind direction. The public was fascinated by this map. Henry noted that tourists who viewed it "all appear to be specially interested in knowing the condition of weather to which their friends at home are subjected at the time". Henry also experimented with using the map for weather forecasting. He noted, for example, that "if a black card [disk] is seen in the morning on the station at Cincinnati, indicating rain at that city, a rain storm may confidently be expected at Washington at about seven o'clock in the evening". Henry had enough confidence in this rule that he would postpone evening lectures at the Smithsonian on days when Cincinnati had rain in the morning.

On 23 August 1856, the Eighth Annual Meeting of the American Association for the Advancement of Science (AAAS) took place in Albany, New York. Henry presented a paper written by Mrs. Eunice Foote, entitled "Circumstances affecting the Heat of the Sun's Rays" (as a female, Foote was not allowed to present her own paper to the AAAS!). In her short paper, Foote described her experimental demonstration of the effect of solar radiation on various gases. She wrote "On comparing the Sun's heat in different gases, I found it to be in hydrogen gas, 104° [Fahrenheit]; in common air, 106°; in oxygen gas, 108°; and in carbonic acid gas [i.e. CO₂] 125°. She concluded that CO₂ had the power to warm the atmosphere: "An atmosphere of that gas [i.e. CO₂] would give to our Earth a high temperature; and if as some suppose, at one period of its history the air had mixed with it a larger proportion than at present, an increased temperature from its own action as well as from increased weight must have necessarily resulted." John Tyndall's work of just a few years later would expand upon Foote's results.

Henry also provided weather observations to the Washington Evening Star which began publishing daily weather conditions at nearly twenty different cities in May 1857. This was one of the earliest examples of the popular newspaper weather page.

Henry also advocated a system of storm warnings and wrote in his annual report for 1857 that he hoped to arrange with telegraph companies "to give warning on the eastern coast of the approach of storms".

By around 1860 the meteorological network had grown to include more than 600 volunteer observers in Canada, Mexico, Latin America and the Caribbean as well as the United States. The mass of weather observations received at the Smithsonian during the 1850s formed a large data base that had to be checked and interpreted. Henry hired Professor James H. Coffin of Lafayette College in Easton, Pennsylvania to carry out this work. In 1861 Coffin published the first of two volumes of climatic data and storm observations based on the reports for 1854 through 1859.

The American Civil War almost derailed Henry's meteorological work. He wrote in 1861 that the project "suffered more from the disturbed condition of the country than any other part of the operations of the Smithsonian establishment." Weather reports had to compete for telegraph time with public war-related traffic. All reports from the South were cut off. After the war, in his annual report for 1865, Henry called on the federal government to establish a national weather service capable of issuing storm warnings and other weather predictions. At roughly the same time other countries were also moving toward their own national weather services (e.g England under Fitzroy and France under LeVerrier). In 1870 Congress transferred the responsibility for storm warnings and weather predictions to the US Army's Signal Service. By 1874, Henry had convinced the Signal Service to take over the volunteer observer system as well. In 1891, the newly-formed US Weather Bureau took over all the weather-related work of the Signal Service. It later became the National Weather Service, in which Henry's vision and leadership live on today.

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