Page:Popular Science Monthly Volume 3.djvu/82

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72
THE POPULAR SCIENCE MONTHLY.
THE SHERMAN ASTRONOMICAL EXPEDITION.
By EMMA M. CONVERSE.

SCIENTIFIC observers have long seen the importance of securing a position elevated above the fogs and impurities of the atmosphere at the sea-level, for the purpose of making more accurate astronomical and meteorological observations. Accordingly, Prof. Peirce, the Superintendent of the Coast Survey, petitioned Congress for means to carry out such an undertaking. Congress made an appropriation of $2,000 for this special object, independent of the geographical and topographical constants of the station.

Sherman, in Wyoming, situated on the highest point of the Union Pacific Railway, and on the Rocky Mountain range, was agreed upon as an eligible and convenient locality for the scene of operations; and the months of June, July, and August, 1872, were devoted to the work.

The party consisted of General R. D. Cutts, an experienced officer of the Coast Survey, who had charge of the expedition, Assistant Mosman, Aid Colonna, Prof. Young, Prof. Emerson, and Mr. Mead, of Dartmouth College. There were also a photographer, a mechanician, and two servants. The party had, as an escort, about a dozen soldiers from Fort Russell, at Cheyenne, who assisted in keeping the hourly series of meteorological observations, and were detailed to serve as a protection from possible attacks of hostile Indians.

It was not until July that the members from Dartmouth College were able to join the expedition. The trustees of the college had loaned their valuable telescope for the occasion. It has an aperture of 9 4/10 inches, and a focal length of 12 feet, with clock-work, and the usual accompaniments, and is fitted with an automatic spectroscope, having a dispersive power of 13 prisms. This telescope is one of the best in the county in optical perfection, and in convenience and handiness of mounting.

The summit of a slight elevation was chosen as an eligible locality for occupation. It was a short distance from the railroad-station, and about 40 or 50 feet above the track. Three shanties of rough boards were erected as observatories, one for the transit instrument, one for the meteorological apparatus, and one for the equatorial telescope. The altitude of the observatory is 8,300 feet above the level of the sea, the latitude a little more than 44°, and the longitude about 28° west from Washington.

It was thought that Sherman combined unusual facilities for accomplishing the desired object of the expedition, which was to test the advantages of a great elevation upon astronomic, and especially spectroscopic, work. The currents, impurities, and reflective power of the atmosphere at the sea-level, interfere greatly with studies of this kind,