deposit. I ought to have cleaned them out some time ago."
Ned gave a hasty glance at the gage which showed the gas pressure. It registered six hundred pounds now, having risen a hundred in a short time.
"And she'll go up, sure, at eight hundred," murmured Ned, as he held the light steadily on the smugglers' aircraft. "Well, if Tom sticks to the chase, I will too, but I think it would be better to go down, open up everything, and let the gas escape. We could get the rascals later."
Tom, however, did not seem to think so, for he kept on with his task, working away at the pipes, trying to force the obstruction out, so that the gas from the generator would flow into the bag. At the same time he tried to shut off the generating apparatus, but that had become jammed in consequence of the pipe clogging, and the powerful vapor continued to manufacture itself automatically in spite of all that Tom could do.
The only safe way out of the danger, unless he could remove the obstruction, was to descend to earth, and, as Ned had said, open every outlet. But to have done that in mid-air would have been dangerous, as the large volume of gas, suddenly liberated, would have hung about the airship in a cloud, smothering all on board. If they were on
