"Hold your ship. I propose to come aboard and search her. In the name of the United States Government!"
Mr. Henderson took the radio telephone out of Mark's hand and replied:
"We wish to know who and what you really are. We will not put ourselves in your power without knowing. We are amply armed."
"Don't you dare to fire upon a United States officer in the discharge of his duty," cried the voice from below, and now the strange airship was much nearer to them. "Who do you claim to be?"
"This is the Snowbird, from Easton, Maine, She is manned by her builders, Darrow and Sampson. She carries as passengers Washington White, Andrew Sudds and Amos Henderson," declared the professor, in reply. "And she is bound for Alaska."
"Well, well!" exclaimed the voice of their pursuer. "That may all be so. But I have my suspicions. I am Ford, special agent of the Department of Justice. Stand by. Now I am coming aboard."
At a nod from the professor, Mark had already brought the Snowbird to a halt. She lay floating, with all planes extended and without motion of propellers, poised over the summit of Mt. Katahdin.
The descending moon threw its beams over the height and revealed to the vaguely anxious occupants of the Snowbird, the other machine darting up from below.
This was a craft of much different aspect from their own. It was a great deal smaller and apparently without half the power possessed by the one built by Jack and Mark.
She shot into the air above their heads at a swift pace, however, and immediately poised over them. In this attitude Ford, as he called himself, had the occupants of the Snowbird completely at his mercy. A bomb dropped upon the huge flying machine would have blown her to pieces. Or, with a gun, he could have picked off one after another of the five people below.