Page:Popular Science Monthly Volume 26.djvu/403

Rh grows with the power of the instrument. Atmospheric troubles are magnified neither more nor less than the objects viewed across them. Thus, Lord Rosse's giant reflector possesses—nominally—a magnifying power of 6,000; that is to say, it can reduce the apparent distances of the heavenly bodies to $1⁄6000$ their actual amount. The moon, for example, which is in reality separated from the earth's surface by an interval of about two hundred and thirty-four thousand miles, is shown as if removed only thirty-nine miles. Unfortunately, however, in theory only. Professor Newcomb compares the sight obtained under such circumstances to a glimpse through several yards of running water, and doubts whether our satellite has ever been seen to such advantage as it would be if brought—substantially, not merely optically—within five hundred miles of the unassisted eye.

Must, then, all the glowing triumphs of the optician's skill be counteracted by this plague of moving air? Can nothing be done to get rid of, or render it less obnoxious? Or is this an ultimate barrier, set up by Nature herself, to stop the way of astronomical progress? Much depends upon the answer—more than can, in a few words, be easily made to appear; but there is fortunately reason to believe that it will, on the whole, prove favorable to human ingenuity, and the rapid advance of human knowledge on the noblest subject with which it is or ever can be conversant.

The one obvious way of meeting atmospheric impediments is to leave part of the impeding atmosphere behind; and this the rugged shell of our planet offers ample means of doing. Whether the advantages derived from increased altitudes will outweigh the practical difficulties attending such a system of observation when conducted on a great scale, has yet to be decided. The experiment, however, is now about to be tried simultaneously in several parts of the globe.

By far the most considerable of these experiments is that of the "Lick Observatory." Its founder was from the first determined that the powers of his great telescope should, as little as possible, be fettered by the hostility of the elements. The choice of its local habitation was, accordingly, a matter of grave deliberation to him for some time previous to his death. Although close upon his eightieth year, he himself spent a night upon the summit of Mount St. Helena, with a view to testing its astronomical capabilities, and a site already secured in the Sierra Nevada was abandoned on the ground of climatic disqualifications. Finally, one of the culminating peaks of the Coast Range, elevated 4,440 feet above the sea, was fixed upon. Situated about fifty miles southeast of San Francisco, Mount Hamilton lies far enough inland to escape the sea-fog, which only on the rarest occasions drifts upward to its triple crest. All through the summer the sky above it is limpid and cloudless; and, though winter storms are frequent, their raging is not without highly available lucid intervals. As