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Maryland's National Register Properties

Photo credit: Catherine A. Masek, 05/1991
Gaithersburg Latitude Observatory
Inventory No.: M: 21-141
Date Listed: 7/12/1985
Location: 100 DeSellum Avenue, Gaithersburg, Montgomery County
Category: Building
Period/Date of Construction: 1899
Architect/Builder: Architect: Edwin Smith
NHL Date: 12/20/1989
Description: The Gaithersburg Latitude Observatory is a small, 13-foot-square one-story building. There is a wooden louver-covered gable roofed entrance porch on the west facade. The original porch door is missing. There is a small shed-roofed ell on the east side. The building has a concrete mortar and fieldstone foundation. The gable roof consists of two sections that move apart on wheels exposing the center interior of the building. The roof is constructed of inch tongue-and-groove board. In the eaves, the rafter ends are cut back and covered by a tilted fascia board. A decorative wooden five-pointed star is mounted in the center of each gable end. The inner wall plates consists of double 2x8s resting on edge. On the north and south walls, these plates extend about three feet beyond the building to support the roof in its open position. These extended plates are capped with 4x4s supporting the metal U-track in which the roof wheels travel. Parallel to the U-track, about six inches into the building and down about four inches, are a pair of 1" thick iron rods. These extend the length of the north and south plates, piercing the east and west walls. They are moved from inside the building. Each section can be moved independently by a rope and pulley system. There are two decorated ventilators, one on each roof section near the center of the building. As part of the decoration, a metal five-pointed star caps each ventilator. The building is double walled, the inner wall consisting of 4x4s overlaid with tongue-and-groove boards on the inside. There is a 9" space between the walls. The outer wall consists of 4x4s covered on the outside with horizontal framed louvers. The outside walls are connected to the inner walls only at the building corners, the entrance, and the door to the east ell. The inner and outer sills appear to rest on the foundation. The exterior wall ends at the ground in a beveled wooden water table. There is a double floor in the main room with a concrete pyramid-shaped pier in the center of the dirt floor that is sunk four feet below the floor and tapers as it extends up to about waist height. The observing telescope and instruments were mounted on it. The telescope is now in storage in Corbin, Virginia. The southern wall has a central section of two by three feet which can be lowered to expose two sliding wooden sashes in the inner wall. About 200 feet to the south of the observatory is the Meridian Mark Pier (azimuth marker), a green metal pagoda-shaped object about four feet high by two feet square, which was used to align the Zenith Telescope. Significance: The Gaithersburg Latitude Observatory is significant for its association with the study of polar motion, and for its symbolic value in representing an important and long-lived program of international scientific cooperation. Established in 1899 by the International Geodetic Association, the International Polar Motion Service was a cooperative effort among scientists worldwide to study the Earth's wobble on its rotational axis. The Gaithersburg Latitude Observatory was one of six observatories around the world (in the United States, Russia, Japan, and Italy) commissioned under this program. Between 1900 and 1960 these observatories were the best source of information on polar motion available to scientists. Data supplied by the six latitude observatories have been used in hundreds of scientific papers and studies investigating the geophysics of the earth. The observatories have enabled geodesists to better understand the size and shape of the earth and astronomers to adjust their observations for the effects of polar motion. In more practical terms, the work done by the observatories contributed to studies attempting to determine earthquake mechanisms and the elasticity of the earth, and to predict climate variations. The space program has also benefited from this work; polar motion study is necessary to determine orbit patterns of spacecraft and satellites, and aids tracking techniques used in deep space navigation. The latitude observatories made a major contribution to science on an international scale. The research undertaken in these small, simple structures not only fueled all work done in earth motion for decades, but transcended the differences of man during times of war and international strain. Despite the location of stations in two Allied nations and two Axis nations during World War II, cooperation between the observatories continued and their important work did not cease. From its construction in 1899 until the obsolescence of man-operated telescopic observation forced its closing in 1982, the Gaithersburg Latitude Observatory played an integral role in this important scientific endeavor.
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