Now they were circling high over the heads of the populace, with one engine shut off and the speed of the other much reduced.  In graceful, pretty circles the Sky-Bird began to spiral her way downward, John's eyes fastened upon the big white T of the familiar airdrome.  As they came down, people in the outlying districts rushed madly toward the field, and the streets everywhere were choked with the concourse pouring toward the center of attraction.