keep dark until I can see what's the matter. We must leave here before daylight."
"Suppose we can't?" asked Mr. Damon. "The crowds will be sure to see us then, anyhow."
"I am pretty sure we can get away," was the opinion of the balloonist. "Even if our gas container is so damaged that it will not sustain us, we are still an aeroplane, and this roof being flat will make a good place to start from. No, we can leave as soon as this storm lets up a little."
"Then I'm going to have a look and find out what sort of a building this is," declared Tom, and, while Mr. Sharp began a survey, as well as he could in the dark, of the airship, the young inventor proceeded cautiously to ascertain the extent of the roof.
The rain was not coming down quite so hard now, and Tom found it easier to see. Mr. Damon, finding he could do nothing to help, went back into the cabin, blessing himself and his various possessions at the queer predicament in which they found themselves.
Flashing his light every few seconds, Tom walked on until he came to one edge of the roof. It was very large, as he could judge by the time it took him to traverse it. There was a low parapet at the edge. He peered over, and an expanse of dark wall met his eyes.
