Ogilvy told him all that he had seen.  Henderson was a minute or so
taking it in.  Then he dropped his spade, snatched up his jacket, and
came out into the road.  The two men hurried back at once to the
common, and found the cylinder still lying in the same position.  But
now the sounds inside had ceased, and a thin circle of bright metal
showed between the top and the body of the cylinder.  Air was either
entering or escaping at the rim with a thin, sizzling sound.