Page:Popular Science Monthly Volume 10.djvu/586

568 desert in 120° 20' east longitude. No water-courses were found flowing to the eastward; along the twenty-fourth parallel to 127° east longitude, the country was found to be an open desert.

"This very imperfect survey of the geographical work of the world, when regarded as the work of a single year, justifies, I think, what I said in my last address—that we are living in a great geographical age."



T is not a little curious that the great body which for ages has been proverbial for its changeableness should have at last come to be looked upon as the most unchangeable of bodies. When the earth was regarded as constituting the universe, and the heavenly bodies as mere exhalations from it, the moon was, of course, believed to be nothing but a meteor—a great lantern hung in the sky to illuminate and rule the terrestrial night; but, when modern astronomy had established the idea that the earth is but a moving planet, and the planets themselves great orbs like our own globe, speculation inevitably arose in regard to their condition. It was then concluded that the moon may be like the earth, with its oceans, plains, mountains, atmosphere, vegetation, and inhabitants; and this idea long prevailed as a part of the great doctrine of the plurality of worlds. But an opposite opinion at length grew up among astronomers, which has been greatly strengthened in recent years. This change of view has been largely ascribed to the celebrated astronomer Mädler, who made a very forcible statement of the differences and contrasts between the condition of the moon and that of the earth, and pointed out that the current view that the moon may be a copy of the earth is impossible. These views crept into astronomical text-books, and gradually led to the conviction that the moon is a sort of played-out or defunct planet, destitute of air and life—a mere mass of rocks and cinders, cold, lifeless, and unchangeable.

But although this view is still current among astronomers in general, there is a class of astronomers (selenographers, as they are called) who have studied the lunar surface with long and profound attention, and to whom we are indebted for our present knowledge of our satellite, who hold a different view. They agree in the belief that many processes of actual lunar change are in progress, and they have detected the existence of a lunar atmosphere. This conflict of opinion is said to be due to the fact that the labors of selenographers are 