Page:The Music of the Spheres.djvu/318

 far less conspicuous than the Apennines, for not only do these latter mountains reach into a higher altitude but they also are crowned along their 450 miles with some 3000 steep and rugged peaks. The Alps are noted for a remarkable flat-bottomed valley which cuts in a straight line through these mountains for a distance of 80 miles. This valley is from 3½ to 6 miles wide and at least 11,000 feet in depth. Such a long, level strip bordered by gigantic mountains is as unique a formation as the mammoth craters with the towering rims.

The Leibnitz and the Doerfel mountains are on the southern part of the moon near the pole. These mountains are so situated that the light of the sun always shines from their summits, and even during an eclipse they are visible in profile. Some of the peaks on these "mountains of eternal light" are very high, their needle-like points reaching upward for 26,000 to 27,000 feet. It has been estimated that if our mountains on earth were comparatively as high as the mountains on the moon, our earthly mountains would rise to the height of about 15 miles! The height and sharpness of the moon mountains is due partly to the low surface gravity,