"Maybe it's Mars," suggested Mark.
"No, it can't be that planet."
"What is it?" inquired Jack. "Look, the needle went all the way around that time."
Mr. Roumann bent over the gage. Then he consulted some charts of the sky, and made a few calculations.
"Boys, I am afraid we're approaching a large comet," he said gravely. "And, what is worse, it is attracting us toward itself. We are in great danger!"
CHAPTER XIX
ESCAPING A COMET
The two boys looked at the German scientist. He was gazing, as if fascinated, at the swiftly moving needle of the gage that had told of the nearness of the comet.
"How far from it are we?" asked Jack.
"Many thousands of miles," replied Mr. Roumann. "But that distance is nothing compared to the rate at which we are traveling. We are almost certain to crash into it, or the comet will collide with us."