"Here, boys, come over here a minute!" called the fat man.  As they approached, the aviators with him turned from their work.  One, a slender fellow with swarthy skin and a scrubby black mustache, scowled when he looked at John Ross, and as Bob Giddings and Tom Meeks got their eyes on him, they gave an involuntary start, for they recognized in the man the fellow they had seen hanging around the fair-grounds in Yonkers when their machine was in process of construction.