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To the well-informed these flights over the Mediterranean displayed a unique and novel feature. This was the action of the maritime guide-rope—a long, thick rope dangling from the airship with eight or ten feet of its still thicker extremity dragging in the water.

Vertical stability is the life of any balloon, but to the balloon airship that may not waste the little ballast it carries, the problem becomes doubly complicated. Caused by changes in temperature and atmospheric pressure, condensation and dilatation continually react upon each other in the spherical balloon, necessitating continual losses of gas and ballast.

’’Suppose you are in equilibrium at a desired height,’’ M. Santos-Dumont once explained to me. ‘‘Suddenly a small cloud hides the sun for a few moments, and the temperature of the gas in the balloon cools down a little. If the balloonist does not immediately throw out just sufficient ballast to compensate the ascensional force lost by the shrinking of the