The machine had attracted little attention on the route, for it was painted a dull gray, and its aluminum motors gave forth little sound.  It was two merits of the machine, which had been invented by young Leroy, that it could navigate in a clear sky a mile up without being observed from below, and could also run to within a short distance of the earth without making herself conspicuous by the popping of her motors.  The United States authorities are now adapting these two qualities to the government airships to be used in the military service.