A moment's inspection showed that we had stumbled upon the most marvelous work of the forces of crystalization that human eyes had ever rested upon. Some time in the past history of the moon there had been an enormous outflow of molten material from the crater. This had overspread the walls and partially filled up the interior, and later its surface had flowered into gems, as thick as blossoms in a bed of pansies. The whole mass flashed prismatic rays of indescribable beauty and intensity. We gazed at first speechless with amazement. "It cannot be, surely it cannot be," said Professor Moissan at length. "But it is," said another member of the party. "Are these diamonds?" asked a third. "I cannot yet tell," replied the Professor. "They have the brilliancy of diamonds, but they may be something else." "Moon jewels," suggested a third. "And worth untold millions, whatever they are," remarked another. These magnificent crystals, some of which appeared to be almost flawless, varied in size from the dimensions of a hazelnut to geometrical solids several inches in diameter. We carefully selected as many as it was convenient to carry and placed them in the car for future examination. We had solved another long standing lunar problem and had, perhaps, opened up an inexhaustible future mine of wealth which might eventually go far toward reimbursing the earth for the damage which it had suffered from the invasion of the Martians. On returning to Cape Heraclides we found that the other expeditions had arrived at the rendezvous ahead of us. Their members had wonderful stories to tell of what they had seen, but nothing caused quite so much astonishment as that which we had to tell and to show. The party which had gone to visit Plato and the lunar Alps brought back, however, information which, in a scientific sense, was no less interesting than what we had been able to gather. They had found within this curious ring of Plato, which is a circle of mountains sixty miles in diameter, enclosing a level plain remarkably smooth over most of its surface, unmistakable evidences of former habitation. A gigantic city had evidently at one time existed near the center of this great plain. The outlines of its walls and the foundation marks of some of its immense buildings were plainly made out, and elaborate plans of this vanished capitol of the moon were prepared by several members of the party.