the speed lever over a few more notches, and increased the power of the gas machine. Still the Black Hawk did not rise.
"Bless my handkerchief box!" cried Mr. Damon, "what's the matter?"
"I don't know," answered Tom. "We seem to be held fast."
He further increased the speed of the propellers, and the gas machine was set to make vapor at its fullest capacity, and force it into the bag. Still the craft was held to the earth.
"Maybe the gas has no effect in this climate," called Ned.
"It can't be that," replied Tom. "The gas will operate anywhere. It worked all right today."
Suddenly the airship moved up a little way, and then seemed to be pulled down again, hitting the ground with a bump.
"Something is holding us!" cried Tom. "We're anchored to earth! I must see what it is!" and, catching up his electric rifle, he dashed out of the cabin.
