“Then you are making good progress toward science,” I replied. “One last look, now, at the photograph of the Old Moon’s sickle, and then we had better postpone our examination of the large photographs, showing certain particularly interesting districts on the moon, until to-morrow morning. There is here another interesting point for artists to note. The convex side of the sickle of the Old Moon, or the New Moon, is always an arc of a circle, but the concave side is never circular although it is often thus represented. The concave side, neglecting its irregularities arising from the differences of level and of brilliancy of the lunar surface, is elliptical in outline, that is to say, it is a semicircle viewed obliquely.” “Whatever its geometry may be,” replied my friend, “it is certainly very beautiful. Good night, and I shall demand to see those large photographs before the sun is very high to-morrow.” ------------------------------------------------------------------------ IV GREAT SCENES ON THE MOON ------------------------------------------------------------------------ IV GREAT SCENES ON THE MOON MY friend did not leave me in doubt on the following morning as to the genuineness of her interest in her new studies. The shadows of the trees in the park were yet as long drawn out as the silhouettes of lunar peaks at sunrise, when we resumed our place under the elm, and, at her request, I opened once more my portfolio. “The series of photographs that we are now about to examine,” I began, “are on so large a scale that only a selected part of the moon is seen in each of them. But within the restricted limits of these pictures the amount of detail shown is truly astonishing, far more indeed than can be found on the most elaborate lunar charts. These photographs were made by Mr. Ritchey with the great 40-inch telescope of the Yerkes Observatory. Many more besides those that we are going to look at were taken by him, but I have selected, where choice was difficult, six which seemed to me to be of special interest. We shall begin with one which covers the larger part of the _Mare Nubium_, in the southeastern quarter of the moon. You certainly must remember the _Mare Nubium_, for it forms the head of the ‘dark woman’ whom you discovered in the moon last evening, and if you will hold this photograph at arm’s length you will see that her face is unmistakably stamped upon it.” “I am greatly flattered,” she replied, “that you should remember my discovery so well. I begin to feel hopeful that it may yet find a place in the books.” “It certainly is as deserving of such a place as many things that get into books. You ought to find a suitable name for this woman in the moon.”