Our friends returned to the Sky-Bird.  In a few minutes Bob, who had climbed on top of the fuselage to test the helium valves, came down and said: "Something new is going on over in our neighbor's yard, fellows. When I was up there I could see right over the natives' heads, and I noticed Chuck Crossman and Pete Deveaux hunting around the field till they found half-a-dozen rocks as big as a football, and they put these in the cabin of the _Clarion_.  Wonder what on earth they intend to do with those?"