Some Interesting Craters on the Moon.
Aristillus is about 34 miles in diameter, and 10,000 feet deep. In the center of this deep cavity rises a massive many-peaked mountain whose base is often lost in the darkness of the crater's shadows. Autolycus, south of Aristillus and somewhat smaller, is 23 miles in diameter with a floor somewhat depressed below the country which surrounds it.
Some interesting Craters on the Moon.
On the "shore-line" of Mare Imbrium, north of Archimedes, Aristillus and Autolycus, and not far from the "Valley of the Alps," lies Plato, one of the most easily found craters on the moon. Plato is a very huge oblong crater, 60 miles in diameter and containing an area of 2,700 miles. Its floor is exceptionally dark and flat and forms a striking contrast with the bright border of mountains which surround it. Quite a number of minute craterlets have been distinguished on its floor.
The southern hemisphere of the moon, particularly as one approaches the region about the southern pole, is pitted with such a bewildering number of both large and small craters that astronomers say that it is relief to the eye to study the comparatively smooth, shaded portions of the globe after having gazed for any length of time at the crowded mass of detail in this wild and rugged region. The two craters in the southern hemisphere that are perhaps the easiest for the amateur to locate are Clavius, an enormous crater near the mountains at the southern pole, and Tycho, just below it, with its wonderful streaks, or rays.
Clavius is a crater of gorgeous depth and has an area of 16,500 miles. Around its walls and on its floor are many secondary craters, while from its center rise tall mountain peaks, one of which reaches 24,000 feet above the bottom of one of its included craters.
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."