Page:Popular Science Monthly Volume 19.djvu/535

Rh  points towering peaks from fifteen to twenty thousand feet above the level of the dark plain.

The Mare Imbrium, also lying in the north quadrant, is the largest of the dark ring-plains of the moon. The lunar Carpathian and Apennine ranges bound it on the south, the Caucasus and Alps on the west, and on the north the lofty highlands of Plato and the Sinus Iridum. It has a length of seven hundred and fifty miles, and a breadth of six hundred and seventy-eight.

One of the most wonderful and mysterious features of the moon, and seen on the southern quadrant, is Tycho, the center of the principal streak system. From its mountain-walled plain issue streams of radiance like rivers of silver; some of these "rilles" flow for a length of a thousand miles. The southern portion of the moon is a mass of old craters, ring-plains, valleys, hills, and ridges; with its radiant streak system and diversity of formations it is the most interesting part of the lunar surface.

When completed, this series of paintings will present not only a worn-out world in miniature, but, if one may credit the great astronomers of our day, the painted prophecy of the far-off future of our own earth, when it shall have cooled off, and all the bustling, battling throngs of humanity be as its own clay!



N the course of some recent inquiries into visual memory, I was greatly struck by the frequency of the replies in which my informants described themselves as subject to "visions." Those of whom I speak were sane and healthy, but were subject notwithstanding to visual presentations, for which they could not often account, and which in a few cases reached the level of hallucinations. This unexpected prevalence of a visionary tendency, among persons who form a part of ordinary society, seems to me suggestive and worthy of being put on record. In a previous article I spoke of the faculty of summoning scenes at will, with more or less distinctness, before the visual memory; in this I shall speak of the tendency among sane and healthy persons to see images flash unaccountably into existence.

Many of my facts are derived from personal friends of whose accuracy I have no doubt. Another group comes from correspondents who have written at length with much painstaking, and whose letters 