46 MOUNTAIN OBSERVATORIES IN AMERICA AND EUROPE. 



Sherman was by no means an ideal station, but the observations of 

 Professor Young, and especially the spectroscopic observations of the 

 sun, showed the immense advantages of a high-level station far above 

 the dust and mists of the lower atmosphere, when the condition of 

 steadiness was added to that of transparency. 



It is not necessary to gi^•e an account of these spectroscopic observa- 

 ti()ns which are well known to all interested,* but it may be mentioned 

 tliat at Dartmouth College Professor Young had been able to map 103 

 spectral lines which are reversed in the chromosphere. In six weeks 

 at Sherman all these were verified and 170 new ones added. This is a 

 striking proof of the excellence of the atmospheric conditions and of 

 the assiduity of the observer. 



EocKY Mountain Stations in Central Colorado. 



During the summer of 1873 I spent several weeks in Colorado, 

 always at altitudes above 5000 feet, and frequently at 9000 and 10,000 

 — and occasionally at heights of 13,000 feet and even more. The 

 region around Pike's Peak, on its flanks, and throughout the South 

 Park, was pretty thoroughly traversed — at Manitou, Florissant Valley, 

 Central City, Idaho Springs. Fairplay, Mount Bross (near Mt. Lincoln), 

 Canon City, etc. In July, 1878, this region was again visited and I 

 made a stay of about a week at Central City (84:00 feet) and vicinity. 

 A third visit was made in December, 1885. On all these occasions com- 

 })arisons were made (with the naked eye, opera-glasses, or small tele- 

 scopes) between the conditions of vision at Washington and those in 

 the Eocky Mountains. Objects with which I was familiar (usually 

 groups of stars, as the region bounded by the four brightest stars of 

 Ursa major, of Lyra, etc.) were studied and mapped at both stations to 

 determine the relative transparency of the air in the East and in the 

 Eocky Mountain region in question ; and careful notes were made of the 

 relative amounts of twinklino- of the stars at both stations. 



During six journeys across the continent from the east to the Pacific 

 and return in the years 1881, 1883, 1885, 1886 similar exjDcriments 

 were made, whenever possible, both on the Southern Pacific and Union 

 Pacific railways. All these observations taken together simply con- 

 firmed the conclusions reached in 1873, which I then reported to the 

 Superintendent of the U. S. Naval Observator}^ and to astronomers in 

 Washington. These conclusions briefly stated were : 



1. The transparency of the air at heiglits of 6000-14,000 feet in 

 this Eocky Mountam region was always markedly superior to that at 

 eastern stations, as was to be expected. 



* See Professor Young's book , The Sun. 



