The Signal Service

The idea of using the telegraph to convey meteorological information was first suggested by Professor Henry of the Smithsonian Institute in his report for 1847. The thought did not at once produce permanent results, but gradually and surely it attracted attention and support, and finally, on February 9, 1870, Congress authorized the employment and organization of a Signal Service Corps, under the direction of the Secretary of War, for the purpose of taking and recording observations and displaying signals.

Regular reports were first received at Washington at 7.35 A. M., November 1, 1870, from twenty-four stations then established. The reports were tabulated and sent to various cities at 9 A. M., and thus the work began. The object of the service is to obtain such information from all parts of the country as will enable the observers to forecast the condition of the weather several hours in advance. The rise and fall of rivers and the tides are noted, atmospheric and weather changes of every kind observed, and the character and location of clouds examined. All these observations are carefully grouped and studied, and the synopsis and probabilities made up therefrom.

In addition to reports from the principal cities lying along the chief rivers, lakes and sea-boards, and from posts of observation occupying every possible altitude, including Mt. Washington in the east and Pike's Peak in the west, reports are also obtained at Washington from the Canadian Provinces, and from the British, Russian, and Turkish governments. The entire corps, as a detachment of the United States Army, is under command of the chief signal officer of the army, whose headquarters are at Fort Myer, Va., at which place there is a school of instruction. The observers, to a certain extent, are under military rule, but are enlisted solely for this service, and must be fitted by education and character for the important position they occupy. The central office is with the War Department at Washington.

The office of observation at Detroit was located in the Bank Block, corner of Congress and Griswold Streets, until February 8, 1881, when it was moved to the Board of Trade Building, corner of Jefferson Avenue and Griswold Street. It was established by Sergeant Allen Buel, and reports commenced November 1, 1871, just one year after the service was inaugurated. The official number of the observatory is thirty-six; it is in charge of one sergeant with two assistants. Five observations of the weather are taken daily; two for record and comparison, at 10.36 A. M. and 6.36 P. M., and three for telegraphic transmission to the central office at Washington, at 6.36 A.M., 2.36 and 10.36 P.M. Experience has shown that the mean or average condition of the weather is best obtained at these hours.

Telegraphic observations are taken at all stations throughout the country at the same moment of actual time. The standard hours are 7.35 A. M., 3 and 11 P. M., Washington time, due allowance being made at each station for difference of longitude. An observation of the surface and bottom temperature of the river is also taken daily at 1.36 p. M. The taking of an observation consists in reading the barometer, the thermometer, hygrometer, anemometer, and anemoscope, and measuring the water in the rain-gauge after rainfall; the direction, kind, and rate of motion of the upper and lower strata of clouds are also recorded. All barometrical observations are corrected for temperature, elevation above sea-level, and instrumental error. The elevation for which the barometer is corrected at Detroit is 661.43 feet, it being located 86.15 feet above the city base or bench mark designated on the water-table of the old Water Works Engine-house at the foot of Orleans Street, which is computed as 575.28 feet above sea-level.

From the barometer is obtained the weight or pressure of the atmosphere. From the reading of the hygrometer, which, being but a wet-and-dry-bulb thermometer, may be better defined as a psy-chrometer, is deduced the amount of moisture in the atmosphere. The ratio which the amount of moisture actually present in the air bears to the amount which the air would contain if saturated, is the relative humidity of the atmosphere.

The anemometer, or wind-gauge, measures the velocity and indirectly the force of the wind. This, by means of a self-registering attachment, worked conjunctively by clock-work and a galvanic battery, gives the velocity in miles per hour for each consecutive hour of the day.

The anemoscope, in common parlance a weather-vane, is attached to the ceiling of the room, and is controlled by apparatus on the roof of the building. The direction of the wind at any time can be told by a mere glance at the ceiling of the room.

About one hundred and fifty telegraphic reports are received at this office from other stations, an equal number morning, afternoon, and midnight. They are received in cipher, translated into ordinary language, and distributed at prominent points in the city, and furnished gratuitously to local papers for publication. The "Probabilities" are received from the central office at midnight. From them the "Farmers' Bulletins" are compiled. Nearly four hundred of the bulletins are printed; a few are reserved for local distribution, and the rest dispatched by early mail to the postmasters of the various towns lying on or adjacent to the railroad lines leading from the city. Reports were first sent from Detroit to the post-offices on July 21, 1873. It is designed to so distribute the bulletins as to insure their receipt by each postmaster before twelve o'clock at noon.

The issuing of these "Synopses and Probabilities" was commenced February 19, 1871 ; they give the probable weather conditions for the eight hours succeeding their issue. The report of the service for the year ending June 30, 1882, shows that eighty-eight per cent of its probabilities for the year were verified. Fourteen weather-bulletins, giving the state of the weather, direction of wind, height of barometer, temperature, and velocity of wind in miles per hour at all stations from which reports are received, are made out daily at 9 A. M., and posted in various parts of the city with the probabilities. A large weather-map, hung in the rooms of the Board of Trade, and changed each morning, gives the same information as the smaller bulletins, with the addition of the relative humidity. A daily journal is kept in which are noted all unusual atmospheric appearances and disturbances, phenomena of storms, the occurrence of meteoric and auroral displays, etc.

Cautionary signals are displayed when ordered from Washington. They consist of a red flag with black square in the center by day, and a red light by night, hoisted from the roof of the building in which the office is located. Either of these signals indicate that a storm is probable, and that mariners and others interested in out-door work should make preparations accordingly. The first storm warning given was for the lakes, and was ordered on November 8, 1870. These signals have been in regular use since October 23, 1871. Each signal holds good for about eight hours from the time it is first displayed. What is known as the northwest (wind) signal consists of a white flag with black square in the center, hoisted over the cautionary signal; it indicates that winds may be expected from the north or west. The cold wave signal consists of a white flag with black square center, and it indicates that a cold wave is advancing from the west; this signal was established August 6, 1884. When important storms are moving, extra telegrams are sent, and by means of the various maps, bulletins, and signals, many lives have been saved and much property preserved from destruction.

The observers in charge have been: Allen Buel, from October 12, 1870. to October 20, 1871; F. Mann, October 20, 1871, 10 April 8, 1873; W. Finn, April 8, 1873, to July 16, 1875; Henry Fenton, July 16, 1875, to August 22, 1875; Theodore V. Van Husen, August 22, 1875, to February 24, 1879; C. F. R. Wappenhaus, from February 24, 1879; E. Russell Brace, from March, 1883 ; Norman B. Conger, from January, 1884; F. W. Conrad, from October, 1886.

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