One fact these experiments seemed to establish was, that when rain is falling from an overcast sky, there is always a higher layer of clouds overhanging the lower stratum. Nothing surprised Mr. Glaisher more than the extreme rapidity with which the whole sky, up to a vast height, could fill up entirely with clouds at the approach of a storm. Another point noted was that, when a wind is blowing, the upper portion of the current always travels faster than that next the ground. This is due, of course, to the obstacles the wind meets as it sweeps over the earth, and which check its onward progress. These, and very many other facts of the greatest interest to the meteorologist, were the outcome of Mr. Glaisher’s experiments. Later voyages of a similar kind have added greatly to our knowledge of the condition of the air, and it seems certain that in the future the balloon will be much more used by scientific men, and by its means they will be able to predict the weather more accurately and further ahead than at present, and learn many other things of which we are now in ignorance. CHAPTER V THE BALLOON IN WARFARE But there is another practical use for the balloon to which we must now refer, and that a most important one--its employment in war-time. It was not long after the invention of this ship of the skies that soldiers began to realise what a valuable aid it might be to them in times of battle, enabling them to see inside a camp, fort, or beleaguered city, or watch the enemy’s movements from afar off. The opportunity for first putting the matter to the test very soon arose. Within a very few years of the earliest balloon experiments in France there commenced in that very country the dreadful French Revolution, and soon the nation found itself at war with all the world, and forced to hold its own, alone, against the armies of Europe. This danger quickened the minds of all to the importance of making use of every possible means of defence in their power. It was suggested that the newly discovered balloon might be turned to account, and immediately a school for military ballooning was established near Paris. Fifty young military students were trained in the new art, and suitable balloons were provided. The value of their work was soon apparent. In June 1794 was fought the battle of Fleurus, between the French and Austrians. Before the fight a balloon party had carefully observed the position of the Austrian forces, and, through the information they gave, the French were able to gain a speedy and decisive victory. In this way, and at this early stage, the value of the war balloon was at once established.