"Ah, boys," remarked the older professor, as he caught sight of them,
"I hope I didn't disturb you by sending for you."

"No; Jack and I were only having a red-hot discussion about diamonds on
the moon," said Mark, with a laugh.

"Diamonds on the moon!" exclaimed Professor Henderson.

"Diamonds on the moon?" repeated his friend, Prof. Santell Roumann. "Is
this a joke, boys?"

"Mark thinks so, but I don't!" cried Jack, enthusiastically. "Look
here, Professor Henderson, and also Mr. Roumann. Here is one of the
newspapers that we brought back with us in our projectile, the
_Annihilator_, after our trip to Mars. I have been translating some of
the articles in it, and to-night I came across one that told of a trip
made by some of the inhabitants of Mars to the moon, in a sort of
projectile, like ours, only more on the design of an aeroplane.

"They landed on the moon, the article states, and found a big field, or
deposit, of Reonaris, which I claim are diamonds. Mark says I'm wrong,
but, Professor Henderson, isn't Reonaris to the Martians what diamonds
are to us?"

"It certainly is," agreed the older scientist, and he looked for
confirmation to his scholarly companion.

"Reonaris is substantially a diamond," said Professor Roumann. "It has
the same chemical constitution, and also the diamond's hardness and
brilliancy. But I don't understand how any diamonds can be on the