“One reason for that is because this photograph represents them on a much larger scale, and with infinitely more detail. Another reason is that now we are looking at them in the lunar afternoon instead of the lunar morning. We are going to see them represented on a still larger scale, presently, but there are many things in this picture well worthy of study. Advancing from the west, the line of night has fallen over the extreme eastern border of the _Mare Nectaris_, and the shadows thrown by the setting sun point westward. Observe how beautifully the brightly illuminated terraces and mighty cliffs of the western wall of Theophilus contrast with the black shadow that projects over half of the interior from the sharp verge of the eastern wall. The complicated central mountain is particularly well shown. The loftiest peak of this mountain mass, which covers 300 square miles, is 6,000 feet in height. You will see its shadow reaching the foot of the western wall. Theophilus is 64 miles in diameter, ten miles more than Tycho, and it is deeper than Tycho, the floor sinking 18,000 feet below the top of the highest point on the western wall. If it were the focus of a similar ray system it would deserve to be called the ‘Metropolitan Crater’ rather than Tycho. Plainly, Theophilus was formed later than its neighbor Cyrillus, because the southwestern wall of the latter has been destroyed to make room for the perfect ring of Theophilus. “The interior of Cyrillus, you will observe, is very different from that of Theophilus. The floor is more irregular and mountainous. The wall, also, is much more complex than that of Theophilus. The broken state of the wall in itself is an indication of the greater age of Cyrillus. On the south an enormous pass in the wall of Cyrillus leads out upon a mountain-edged plateau which continues to the wall of the third of the great rings, Catharina. This formation seems to be of about the same age as Cyrillus, possibly somewhat older. Its wall is more broken and worn down, and the northern third of the inclosure is occupied by the wreck of a large ring. Observe the curious row of relatively small craters, with low mountain ranges paralleling them, which begins at the southwestern corner of Cyrillus and runs, with interruptions, for 150 miles or more. South of this is a broad valley with small craters on its bottom, and then comes an elongated mountainous region with a conspicuous crater in its center, beyond which appears another valley, which passes round the east side of Catharina, where it is divided in the center by a short range of hills. The southeastern side of this valley is bounded by the grand cliffs of the Altai Mountains, which continue on until they encounter the eastern wall of the great ring of Piccolomini, whose interior appears entirely dark in the picture, only a few peaks on the wall indicating the outlines of the ring. The serrated shadow of these mountains, thrown westward by the setting sun, forms one