_Tycho_ is called "The Metropolitan Crater of the Moon," because its brilliant rays stand forth so prominently when the moon is full that all other craters are lost in obscurity. This magnificent crater measures 54 miles from rim to rim with its floor over 3 miles below the highest ridge of the massive mountains which surround it. These mountains are diversified by a series of terraces on their interior slopes while a peak 6000 feet in height rises in the center of its floor. The ray system of Tycho is wholly invisible at the time the sun rises or sets, which is the time when most of the objects on the moon are seen at their best. However when the sun has attained an altitude of 30 degrees, they mysteriously make their appearance, extending for hundreds and some even for several thousands of miles. These rays are never irregular because of interposed obstructions but stretch straight and true in a most remarkable way over mountains, pits and plains. So numerous are these bright rays about the brilliant crater of Tycho that at full moon they may even be located as a patch of light to the unaided eye, although an opera-glass, which brings the moon down to 120,000 miles instead of 240,000, greatly improves the seeing. William H. Pickering, in his book on "Mars," gives some of the latest information concerning Tycho: "The white radiating lines or bands are seen to be due to numerous minute craterlets each giving out a triangular white streamer producing the general effect of a white band. It is probable that this observed regular distribution of the craterlets is due to their lying along invisible cracks radiating from the inner crater. It is much the same as the great volcanoes of the Andes, which stretch in a straight line for over 2000 miles between Peru and the strait of Magellan. The Alaskan volcanoes lie upon a uniformly curved line of nearly equal length.... This line formation is generally considered by geologists to be due to subterranean lines of weakness or cracks in the earth's crust." The moon is considered to be a matured globe, evolutionally old, and it has even been referred to as being nearly dead. Lacking, air, water, life and even the diversion of sound, it surely is at least in but a semi-conscious stage, as worlds go. Mars is also called an old world, but Mars has air, its snow-caps melt in sheets of water, and we view the colors which mark its seasons, across a distance of 50,000,000 miles. The moon looks as it is, seared and old. There have been many theories advanced to explain the abundance of its craters and their peculiar construction, but some modified form of the volcanic action is the only tenable one. No one theory has as yet met with universal approval.