One of the cylinders on the big motor cracked, as they started up next morning, and for some hours they had to hang in the air, suspended by the gas in the container, while Mr. Sharp and Tom took out the damaged part, and put in a spare one, the cylinders being cast separately. It was dusk when they finished, and too late to start up, so they remained about in the same place until the next day.
Morning dawned with a hot humidness, unusual at that time of the year, but partly accounted for by the fact that they were still within the influence of the southern climate. With a whizz the big propellers were set in motion, and, with Tom at the wheel, the ship being about three miles in the air, to which height it had risen after the repairs were made, the journey was recommenced.
"It's cooler up here than down below," remarked Tom, as he shifted the wheel and rudder a bit, in response to a gust of wind, that heeled the craft over.
"Yes, I think we're going to have a storm," remarked Mr. Sharp, eyeing the clouds with a professional air. "We may run ahead of it, or right into it. We'll go down a bit, toward night, when there's less danger of being shot."
So far, on their return trip, they had not been low enough, in the day time, to be in any danger from persons who hoped to earn the five thousand dollars reward.
The afternoon passed quickly, and it got dark early. There was a curious hum to the wind, and, hearing it, Mr. Sharp began to go about the ship, seeing that everything was fast and taut.
"We're going to have a blow," he remarked, "and a heavy one, too. We'll have to make everything snug, and be ready to go up or down, as the case calls for."
"Up or down?" inquired Mr. Damon.
"Yes. By rising we may escape the blow, or, by going below the strata of agitated air, we may escape it."
"How about rain?"