This was perfectly true. The slight obliquity of the Moon's axis, only 1-1/2 deg., keeps the Sun in the same altitude the whole year around. In the equatorial regions he is always vertical, and in the polar he is never higher than the horizon. Therefore, there can be no change of seasons; according to the latitude, it is a perpetual winter, spring, summer, or autumn the whole year round. This state of things is almost precisely similar to that which prevails in Jupiter, who also stands nearly upright in his orbit, the inclination of his axis being only about 3 deg.. But how to account for the _grooves_? A very hard nut to crack. They must certainly be a later formation than the craters and the rings, for they are often found breaking right through the circular ramparts. Probably the latest of all lunar features, the results of the last geological epochs, they are due altogether to expansion or shrinkage acting on a large scale and brought about by the great forces of nature, operating after a manner altogether unknown on our earth. Such at least was Barbican's idea. "My friends," he quietly observed, "without meaning to put forward any pretentious claims to originality, but by simply turning to account some advantages that have never before befallen contemplative mortal eye, why not construct a little hypothesis of our own regarding the nature of these grooves and the causes that gave them birth? Look at that great chasm just below us, somewhat to the right. It is at least fifty or sixty miles long and runs along the base of the _Apennines_ in a line almost perfectly straight. Does not its parallelism with the mountain chain suggest a causative relation? See that other mighty _rill_, at least a hundred and fifty miles long, starting directly north of it and pursuing so true a course that it cleaves _Archimedes_ almost cleanly into two. The nearer it lies to the mountain, as you perceive, the greater its width; as it recedes in either direction it grows narrower. Does not everything point out to one great cause of their origin? They are simple crevasses, like those so often noticed on Alpine glaciers, only that these tremendous cracks in the surface are produced by the shrinkage of the crust consequent on cooling. Can we point out some analogies to this on the Earth? Certainly. The defile of the Jordan, terminating in the awful depression of the Dead Sea, no doubt occurs to you on the moment. But the _Yosemite Valley_, as I saw it ten years ago, is an apter comparison. There I stood on the brink of a tremendous chasm with perpendicular walls, a mile in width, a mile in depth and eight miles in length. Judge if I was astounded! But how should we feel it, when travelling on the lunar surface, we should suddenly find ourselves on the brink of a yawning chasm two miles wide, fifty miles long, and so fathomless in sheer vertical depth as to leave its black profundities absolutely invisible in spite of the dazzling sunlight!"