“In the singularity of the names they chose for objects on the moon,” I replied, “their invention is unrivaled. We shall see some remarkable examples. Of course they are not at all to be blamed for thinking that this oval spot, and other similar ones of much greater magnitude, were seas and oceans. They simply judged by appearance and by analogy. Finding mountains on the moon, they saw no improbability in supposing that there were bodies of water also. They had not the means of knowing, as we know to-day, that there is no water on the moon. Yet, perhaps, they were not so far wrong after all. The _Mare Crisium_ certainly has the look of an empty sea bed, and I should not be willing to assert that ages ago it was not filled with water.” “Like the Great Salt Lake, dried up,” suggested my companion. “Not exactly, for the Great Salt Lake dried up would probably present a surface as white as snow, whereas the _Mare Crisium_ is very dark. It must be admitted, however, that gradually the white deposit would grow darker, and there may be much significance in the fact, which some observers have noticed, that, at times, parts of the dark plains on the moon seem to glitter with minute points of light. Your imagination is at liberty to see deposits of salt there.” “In that case,” said my companion, laughing, “I should prefer to regard the _Mare Crisium_ as resembling that wonderful valley discovered by Sindbad the Sailor, whose floor was sprinkled with diamonds.” “Well,” I replied, “science certainly cannot deny the possibility of diamonds on the moon, for she is _par excellence_ the world of volcanoes, and one of the most striking discoveries of recent years is that of the intimate association existing between ancient volcanic vents and deposits of diamonds. The diamonds of South Africa are found in lava rocks that cooled off ages ago.” “Then I hope that no future Columbus will find a way to the moon, for we should have too many diamonds, and they would lose all their charm.” “That is true, but suppose that not only diamonds but even more beautiful gems should be discovered in the lunar world? You surely would not object to a transethereal traffic bringing them to our doors. However, there is not the slightest prospect that we shall ever be able to go from the earth to the moon. Let us resume our examination of the photograph, and concentrate our attention on the known facts.”