CHAPTER VIII.
GREEN'S GREAT JOURNEY ACROSS EUROPE.
It is probable that at the origin of navigation, man, before he had invented oars and sails, made use of trunks of trees upon which he trusted himself, leaving the rest to the winds and the currents of the water, whether these were known or unknown. There is some analogy between such rude rafts, the first discovered means of navigation on water, and balloons, the first discovered means of navigation in air. But unquestionably the advantage is with the latter. No means have yet been found of directly steering balloons, but by allowing the gas to escape the aeronaut can descend at will, and by lightening his car of part of the ballast he carries he can ascend as readily. It must also be remembered that the currents of air vary in their directions, according to their elevation, and were the aeronaut perfectly acquainted with aerial currents, he might, by raising or lowering himself, find a wind blowing in the direction in which he wished to proceed, and the last problem of aerostation would be solved. That any such knowledge can ever be acquired it is impossible to say; but this much may with safety be advanced, that distant journeys may frequently be taken with balloons for useful purposes.
One of the most remarkable excursions of this kind was that superintended by Green, in 1836, from London to Germany. This journey, 1,200 miles in length, is the longest that has been yet accomplished. Green set out
