Important as atmosphere is to any astronomical investigation, it is all-important to the study of the planets. To get, therefore, within the limits of the United States—limits at the time for several reasons advisable—as steady air as possible, Prof. W. H. Pickering, who had already had experience of Southern California as well as of Arequipa, Peru, proposed Arizona as the most promising spot. Accordingly, Mr. A. E. Douglass left Boston in March, 1894, with a six-inch Clark refractor belonging to the writer, to make a test of the seeing throughout the Territory. From his report, Flagstaff was selected for the observatory site.
Flagstaff, then a town of eight hundred inhabitants, lies on the line of the Atlantic and Pacific Railroad, in the centre of the great plateau of northern Arizona, half way across the Territory from east to west, and two fifths way down from north to south. This plateau, whose mean elevation is between 6000 and 7000 feet, is a great pine oasis a hundred miles or more in diameter, rising some 3000 feet from out the Arizona desert. It culminates in the mass known as the San Francisco Peaks, ten miles north of Flagstaff, whose highest summit rises 12,872 feet above the level of the sea.[9]
The spot chosen was the eastern edge of the mesa (table-land) to the west of Flagstaff. The site lay open to the east and south, and was shielded on the north by the San Francisco Peaks. The distance from the observatory to Mt. Agassiz, the most conspicuous of the Peaks from the Flagstaff side, was about eight miles and three fifths in an air-line, and the distance to the town about a mile and a quarter. As soon as the site was selected, the town very kindly deeded to the observatory a piece of land and built a road up to it.
The observatory stood 350 feet above the town, and 7250 feet above the level of the sea, in latitude 35° 11′ north and longitude 111° 40′ west.
Prof. W. H. Pickering, to whose skill and ability was chiefly due the successful setting up of the observatory, suggested arrangements with Brashear for the use of an eighteen-inch refractor which Brashear had recently constructed,—the largest glass to be had at the time,—arrangements which were accordingly made. He then devised and superintended the construction of a dome intended to be of a temporary character, which worked admirably. The upper part of it was made in sections in Cambridgeport, Mass., and then shipped West, the lower part being constructed according to his specifications on the spot, under the superintendence of Mr. Douglass.
The telescope was supported on one of the Clark mountings. The bed-plate, clock-work, and a twelve-inch telescope were leased of the Harvard College Observatory, and the mounting then altered by Alvan Clark & Sons to carry both the twelve and the eighteen-inch telescopes.
Six weeks from the time ground was broken, on April 23, 1894, regular observations with the eighteen-inch were begun.
The results of the year’s work surpassed anticipation. Details invisible at the average observatory were presented at times with copper-plate distinctness, and, what is as vital, the markings were seen hour after hour, day after day, month after month. First sight; then system; and the one of these factors was as fundamental to the results as the other. Systematic work, first made possible and then properly performed, was the open sesame to that most difficult branch of astronomical observations, the study of our nearest neighbors in the universe.
The chief results obtained were:—
1st, the detection of the physical characteristics of the planet Mars to a degree of completeness sufficient to permit of the forming of a general theory of its condition, revealing beyond reasonable doubt first its general habitability, and second its particular habitation at the present moment by some form of local intelligence;