“You shall not be kept long in expectation. Turn your eyes once more to the _Mare Imbrium_. You will observe that its northern shore consists of a series of curves, each terminating with a promontory projecting into the sea. When looking at it I am often reminded of an entrancing view which I once enjoyed from the summit of Mt. Etna over the island of Sicily. From that great elevation nearly the whole eastern and southeastern coast of the island was visible as upon a map. The indented shore stretched away in long, graceful curves, where the blue Mediterranean contrasted sharply with the yellow sands, and the eye, wandering from Catania to Syracuse, was enchanted with the beauty of those geometric lines. But the winding coast of the _Mare Imbrium_ is far longer than the shores of Sicily, and the mountains and cliffs bordering it are more wonderful than any corresponding scenes on the earth. I wish, particularly, to have you look at the easternmost of the indentations on the northern side of the _mare_. It bears a designation that must surely please your imagination. It is the _Sinus Iridum_, ‘Gulf or Bay of Rainbows.’” “I recognize the work of my old friend the unknown astronomer. Verily he had a poetic soul! And he has written his poem on the chart of the moon, for those to read who can.” “It is a charming landscape that the telescope reveals there,” I said, “even though no rainbows are visible.” “But you will not deny that they may once have spanned that bay and its shores with their exquisite arches?” “No, I shall not deny so pleasing a possibility. I will only say that it lies beyond the ken, and even outside the field, of science.” “Then I regard it as fortunate that _he_ was not too exclusive in his devotion to science, for then he could never have seen the rainbows with the eye of fancy, and your charts would not have been adorned with so delightful a name.”