“Radium,” mocked the echo, but now they were beginning to get used to it.
“Say, it looks as if there was a tide in this river,” remarked Ned, as he noted a sort of high-water mark, where sticks and driftwood were piled up on shore.
“No, that shows where the river rises when there’s a flood, or too much rain,” explained the professor. “The Colorado rises rapidly at times, because the cliffs are so steep that the water from the clouds is almost instantly all poured into the stream. We had better get the ship above flood mark, Jerry, as there may be rain in the night, and we don’t want to go floating down.”
Accordingly the Comet was wheeled farther from shore. Night came on early, in the depths of that gloomy chasm, for they were over a mile below the upper rim of the steep cliffs. But when the big gas lamps had been set aglow, making the circle about the airship one of radiance, and when they were gathered in the cozy cabin, they were all more cheerful.
“Well, we’ll start on a radium hunt the first thing in the morning,” suggested Jerry. And, being inside now, the echo was not so noticeable.
“And I will seek the two-tailed toad,” said the professor. “I wonder if I could not have a look now? Toads come out at night, and if I take a light I may succeed in finding one.”
Supplying himself with an electric torch, the scientist let himself out of the airship. The boys heard him walking about outside, and then they began talking of their trip so far, and speculating as to how it would end.
Suddenly, in the midst of the discussion, there came a cry from outside.