Page:Popular Science Monthly Volume 86.djvu/215

Rh with the proviso, however, that "the same must be located within the state of California."

Just why Lick provided for this telescope and observatory will probably never be known. While I can not recall my authority, I have a very distinct recollection of having heard it stated that the idea was first suggested to him and frequently urged upon him by Professor George Davidson, Concerning this point, however, the director of the Lick Observatory writes,

After having several sites tested the trustees decided upon Mount Hamilton, California, as the best location for the observatory. Active work was begun in 1879, and the observatory was completed and ready for regular work in 1888. The plant cost all but $90,000 of the amount set aside for it. The observatory and this balance were turned over to the regents of the University of California by the trustees June 1, 1888; and since then it has been an integral part of the university.

The principal instruments of this observatory are the great 36-inch refractor, a 6-inch Repsold meridian circle, provided by the Lick Trust, and the 36-inch reflector, a gift from Edward Crossley, Esq., of England. Besides these there is a host of smaller instruments and auxiliary apparatus. I can not go into details here concerning the instruments, but I wish to mention one which has an important bearing upon the subject of this article. It is that the magnifying power of the great refractor may be made to be as much as 3,000 diameters. When one considers that everything in the line of sight of the telescope is magnified by this amount, it becomes evident that, to be efficient, the telescope must be located at a site where the atmosphere through which the line of sight passes is extremely steady, for any little atmospheric disturbance will be magnified to this amount and destroy what is called the "seeing," giving a poorly defined image of the star or object under observation. And it is principally on account of the splendid atmospheric conditions on the Pacific coast, especially on some of the moderately high mountains, which make excellent "seeing" possible that observational astronomy here has been able to make such tremendous strides.

For the efficient use of a great telescope its location must be in a region of great atmospheric calm, where the sky is clear and transparent, with little wind, and where the number of days and nights of a year during which such conditions do not exist is small. For some reason, the "seeing" conditions at Mount Hamilton during the day are not of the best; but at night excellent conditions are found on a large