Moon, whose so-called seas were probably seas in their day, but have now become old sea-bottoms. On Mars the same process is going on, but would seem not yet to have progressed so far, the seas there being midway in their career from real seas to arid depressed deserts; no longer water surfaces, they are still the lowest portions of the planet, and therefore stand to receive what scant water may yet travel over the surface. They thus become fertilized, while higher regions escape the freshet, and remain permanently barren. That they were once seas we have something more than general inference to warrant us in believing.
There is a certain peculiarity about the surface markings of Mars, which is pretty sure to strike any thoughtful observer who examines the planet's disk, with a two- or a three-inch object-glass,—their singular sameness night after night. With quite disheartening regularity, each evening presents him with the same appearance he noted the evening before,—a dark band obliquely belting the disk, strangely keeping its place in spite of the nightly procession of the meridians ten degrees to the east, in consequence of our faster rotation gaining on the slower rotation of Mars. By attention, he will notice, however, that the belt creeps slowly upwards towards the pole. Then suddenly some night he finds that it has slipped