"Of course. I forgot about that," admitted Jack.
"Yes," declared Professor Roumann, "we'll have to be on the lookout for wandering meteors or other stray heavenly bodies. But our instruments will give us timely warning of them. Now, I think we can leave the projectile to herself while I make sure that all the machinery is running smoothly. You boys may stay here if you like, though there isn't much to see."
There wasn't. It was totally unlike taking a trip on earth, where the ever-varying scenery makes a journey pleasant. There was no landscape to greet the eye now. It was even unlike a trip in a balloon, for in that sort of air-craft, at least for a time, a glimpse of the earth can be had. Now there was nothing but a white blanket of mist to be seen, which rolled this way and that. Occasionally it was dispelled, and the full, golden sunlight bathed the projectile. The earth had long since dropped out of sight, for it required only a few seconds to put the _Annihilator_ high up in a position where even the most intrepid balloonist had never ventured.
Mark and Jack sat for a few minutes in the pilot-house, looking out into the ether. But they soon tired of seeing absolutely nothing.
"I wonder what we'll do when we get to the moon?" asked Jack of his chum.
"Why, I suppose you'll make a dive for a hatful of diamonds, won't you? That is, if you still believe that Martian newspaper account."
The boys found the two professors busy adjusting some of the delicate scientific instruments with which they expected to make observations on the trip, and after they reached the moon.
"What is your opinion, Professor Roumann, of the temperature at the moon's surface?" asked Mr. Henderson.
"I am in two minds about it," was the reply. "A few years ago, I see by an astronomy, Lord Rosse inferred from his observations that the temperature rose at its maximum (or about three days after full moon) far above that of boiling water."
"Boiling water!" ejaculated Mark. "Wow! That won't be very nice. I don't want to be boiled like a lobster!"
"Wait a moment," cautioned Mr. Roumann, with a smile. "Later, Lord Rosse's own investigations, and those of Langley, threw some doubts on this. There is said to be no air blanket about the moon, as there is about the earth, so that the moon loses heat as fast as it receives it; and it now seems more probable that the temperature never rises above the freezing point of water, just as is the case on our highest mountains."