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.

Curiously enough, Napoleon would make no use of balloons in his campaigns, and even did away with the balloon school at Paris. The reason given for his prejudice is a curious one. At the time of his coronation a large, unmanned balloon, gaily decorated, and carrying thousands of lights, was sent up from Paris during the evening’s illuminations. It was a very beautiful object, and behaved splendidly, sailing away into the night, amidst great popular rejoicing, until it was lost to sight in the darkness. But at daybreak next morning it was seen approaching the city of Rome, where it presently arrived, actually hovering over St. Peter’s and the Vatican. Then, as if its mission were fulfilled, it settled to earth, and finally fell in Lake Bracciano. But as it fell it rent itself, and left a portion of the crown with which it was ornamented on the tomb of the Roman Emperor Nero. Napoleon, who was always a superstitious man, saw in this extraordinary voyage some dreadful forecast of his own fate. He was much disturbed, and forebade the matter ever to be mentioned in his presence; nor would he henceforward have any more to do with balloons.

Military balloons were used by the French again, however, during their war in Africa in 1830. The Austrians also used them in 1849, and it is said the Russians had them at the siege of Sebastopol in the Crimean War. A Montgolfier balloon was made use of by the French in 1862 at the battle of Solferino; and the Americans also employed balloons during the Civil War a year later. The American war balloons were comparatively small ones, inflated with hydrogen. The hydrogen was manufactured in the way already described, by pouring dilute sulphuric acid upon scrap-iron. For making the gas upon the field two large tanks of wood called “generators” were used. In these the water and scrap-iron were placed and the acid poured upon them, the gas produced being carried to the balloon through pipes, passing first through vessels filled with lime-water to cool and purify it. When on the march four waggons were sufficient to carry the whole apparatus. The inflation, which took some time, was made as close to the scene of action as was considered safe, and when the balloon was once full a party of men could easily tow it about to where it was needed.

But the time when the balloon was most largely and most usefully used in time of war was during the Siege of Paris. In the month of September 1870, during the Franco-Prussian War, Paris was closely invested by the Prussian forces, and for eighteen long weeks lay besieged and cut off from all the rest of the world. No communication with the city was possible either by road, river, rail, or telegraph, nor could the inhabitants convey tidings of their plight save by one means alone. Only the passage of the air was open to them.

Quite at the beginning of the siege it occurred to the Parisians that they might use balloons to escape from the beleaguered town, and pass over the heads of the enemy to safety beyond; and inquiry was at once made to discover what aeronautical resources were at their command.

It was soon found that with only one or two exceptions the balloons actually in existence within the walls were unserviceable or unsuitable for the work on hand, being mostly old ones which had been laid aside as worthless. One lucky discovery was, however, made. Two professional aeronauts, of well-proved experience and skill, were in Paris at the time. These were MM. Godard and Yon, both of whom had been in London only a short time before in connection with a huge captive balloon which was then being exhibited there. They at once received orders to establish two balloon factories, and begin making a large number of balloons as quickly as possible. For their workshops they were given the use of two great railway stations, then standing idle and deserted. No better places for the purpose could be imagined, for under the great glass roofs there was plenty of space, and the work went on apace.

As the balloons were intended to make only one journey each, plain white or coloured calico (of which there was plenty in the city), covered with quick-drying varnish, was considered good enough for their material. Hundreds of men and women were employed at the two factories; and altogether some sixty balloons were turned out during the siege. Their management was entrusted to sailors, who, of all men, seemed most fitted for the work. The only previous training that could be given them was to sling them up to the roof of the railway stations in a balloon car, and there make them go through the actions of throwing out ballast, dropping the anchor, and pulling the valve-line. This was, of course, very like learning to swim on dry land; nevertheless, these amateurs made, on the whole, very fair aeronauts.

But before the first of the new balloons was ready experiments were already being made with the few old balloons then in Paris. Two were moored captive at different ends of the town to act as observation stations from whence the enemy’s movements could be watched. Captive ascents were made in them every few hours. Meanwhile M. Duruof, a professional aeronaut, made his escape from the city in an old and unskyworthy balloon called “Le Neptune,” descending safely outside the enemy’s lines, while another equally successful voyage was made with two small balloons fastened together.

And then, as soon as the possibility of leaving Paris by this means was fully proved, an important new development arose. So far, as was shown, tidings of the besieged city could be conveyed to the outside world; but how was news from without to reach those imprisoned within? The problem was presently solved in a most ingenious way.

There was in Paris, when the siege commenced, a society or club of pigeon-fanciers who were specially interested in the breeding and training of “carrier” or “homing” pigeons. The leaders of this club now came forward and suggested to the authorities that, with the aid of the balloons, their birds might be turned to practical account as letter-carriers. The idea was at once taken up, and henceforward every balloon that sailed out of Paris contained not only letters and despatches, but also a number of properly trained pigeons, which, when liberated, would find their way back to their homes within the walls of the besieged city.

When the pigeons had been safely brought out of Paris, and fallen into friendly hands beyond the Prussian forces, there were attached to the tail feathers of each of them goose quills, about two inches long, fastened on by a silken thread or thin wire. Inside these were tiny scraps of photographic film, not much larger than postage stamps, upon which a large number of messages had been photographed by microscopic photography. So skilfully was this done that each scrap of film could contain 2500 messages of twenty words each. A bird might easily carry a dozen of these films, for the weight was always less than one gramme, or 15½ grains. One bird, in fact, arrived in Paris on the 3rd of February carrying eighteen films, containing altogether 40,000 messages. To avoid accidents, several copies of the same film were made, and attached to different birds. When any of the pigeons arrived in Paris their despatches were enlarged and thrown on a screen by a magic-lantern, then copied and sent to those for whom they were intended.

This system of balloon and pigeon post went on during the whole siege. Between sixty and seventy balloons left the city, carrying altogether nearly 200 people, and two and a half million letters, weighing in all about ten tons. The greater number of these arrived in safety, while the return journeys, accomplished by the birds, were scarcely less successful. The weather was very unfavourable during most of the time, and cold and fogs prevented many pigeons from making their way back to Paris. Of 360 birds brought safely out of the city by balloon only about 60 returned, but these had carried between them some 100,000 messages.

Of the balloons themselves two, each with its luckless aeronaut, were blown out to sea and never heard of more. Two sailed into Germany and were captured by the enemy, three more came down too soon and fell into the hands of the besieging army near Paris, and one did not even get as far as the Prussian lines. Others experienced accidents and rough landings in which their passengers were more or less injured. Moreover, each balloon which sailed by day from the city became at once a mark for the enemy’s fire; so much so that before long it became necessary to make all the ascents by night, under cover of darkness.

They were brave men indeed who dared face the perils of a night voyage in an untried balloon, manned by an unskilled pilot, and exposed to the fire of the enemy, into whose hands they ran the greatest risk of falling. It is small wonder there was much excitement in Paris when it became known that the first of the new balloons made during the siege was to take away no less a personage than M. Gambetta, the great statesman, who was at the time, and for long after, the leading man in France. He made his escape by balloon on the 7th of October, accompanied by his secretary and an aeronaut, and managed to reach a safe haven, though not before they had been vigorously fired at by shot and shell, and M. Gambetta himself had actually been grazed on the hand by a bullet.

Another distinguished man who hazarded the same perilous feat, though for a very different reason, was M. Janssen, a famous astronomer. On the 22nd of December of that year there was to take place an important total eclipse of the sun, which would be visible in Spain and Algeria. It had long been M. Janssen’s intention to observe this eclipse, and for this purpose he had prepared a special telescope and apparatus; but when the time drew near he found himself and his instruments shut up in besieged Paris, with no possible means of escape except the dangerous and desperate hazard of a voyage by sky.

But so great was the astronomer’s enthusiasm for his work, that he resolved to brave even this risk. Taking the essential parts of his telescope with him, and, as aeronaut, an active young sailor, he set sail in the darkness of a winter’s morning, long before dawn, passed safely over the enemy’s lines, and continued the voyage till nearly mid-day, when they sighted the sea, and came down near the mouth of the river Loire, having travelled 300 miles in little more than five hours. Neither Janssen or his telescope were injured in the descent, though the wind was high at the time; and both reached Algeria in time for the eclipse. It must have been a most bitter disappointment to the ardent astronomer, after all his exertions, that when the great day arrived the sun was hidden by clouds, and he was unable to observe the sight for which he had risked so much.

Since the Franco-Prussian war, military ballooning has been largely developed, and now all great armies possess their properly equipped and trained balloon corps. The balloons in use in the British Army at the present day are made, not of silk, but of gold-beater’s skin, a very thin, but extremely tough membrane prepared from the insides of oxen. This is, of course, much stronger and more durable than ordinary balloon fabric, but much more expensive. The balloons are comparatively small ones, of 10,000 feet capacity, and are inflated with hydrogen. The hydrogen is now no longer made upon the field, but is manufactured in special factories, and carried compressed in large steel cylinders. By this means the time occupied in filling the balloon is much reduced, but the weight of the cylinders is very great. As will be remembered, balloons were made of considerable use during the late Boer War. At the siege of Ladysmith they were thought of much value in directing the fire of the British Artillery, and again at Spion Kop and Magersfontein are said to have done good service.

So far we have shown of what use balloons may be in times of peace and war. Every year sees fresh improvements and developments in balloons for military purposes and in those employed for making meteorological and other similar observations; and there is no doubt that great advances may shortly be expected in both these directions. But there is yet another and totally different science to which the balloon may lend its aid, and help greatly to add to our knowledge; and this is the science of geography, or the study of the earth’s surface.

One of the earliest ideas suggested by Montgolfier’s invention was that the balloon might be turned to practical account in the exploring of unknown and inaccessible tracts of the world. It was suggested that in a balloon men might sail over and survey country that they were not able to reach in any other way. Deserts could be crossed in this fashion, forests and mountain ranges, and even the desolate ice-tracts of the North and South Poles.

All this is, in truth, perfectly possible, and another day may be accomplished; but at present great difficulties and dangers stand in the way of exploring by balloon, and up to the present time, with one great exception, no special attempt has been made. It has already been mentioned that both Wise and Green wished to cross the Atlantic by sky, and indeed at the present moment plans are actually being made on the Continent for a similar voyage. This, however, can scarcely be called exploring. Other suggestions which may presently be put to the test are the crossing of the Sahara, and also of another great desert in Central Arabia, into which no white man has ever succeeded in penetrating. Recent expeditions both to the North and South Poles have also taken with them balloons to be used captive for the observation of the state of the ice ahead, and for obtaining wide views around.

The one great attempt at exploring by balloon which has so far been made has, unfortunately, met with hopeless and terrible disaster—this was the ill-fated voyage to the North Pole of AndrÉe and his companions. The idea of reaching the Pole by balloon was first proposed many years ago, and both French and English aeronauts at different times have made suggestions as to the best way in which it might be accomplished. Nothing, however, was attempted until about the year 1894, when M. S.A. AndrÉe, a well-known Swedish balloonist, who had already met with exciting experiences in the air, made up his mind actually to risk the venture.

His plan was to take a suitable balloon, and the apparatus for inflating it, to a place as far north as a ship could safely go, then to fill the balloon and wait for a favourable wind which should carry him right over the Pole and beyond until inhabited country was reached. By the summer of 1896 all his preparations were complete. His balloon was an enormous one, capable of holding 162,000 cubic feet of gas, and was fitted with a rudder sail and a long trail-rope, by means of which AndrÉe hoped to be able to some extent to steer his course across the ice. Two companions were to accompany him on his voyage, and on June 7th the party embarked with all their apparatus, and were conveyed to Spitzbergen.

They landed at Dane’s Island, where their first work was to build themselves a shed. They then got their gas-making apparatus into order, and filled the balloon, and by the 27th of July were all ready for a start. But the wind was contrary, and day after day they waited in vain for a change, until at last the captain of the ship which had brought them warned them they would be frozen in for the winter unless they returned without delay. Very reluctantly, therefore, they abandoned their venture for that year, and went home, leaving behind them the shed and gas-generator for another occasion. The winter passed, and by the end of next May they were back again at Dane’s Island. Their shed and apparatus had suffered damage during their absence, and had to be repaired, and their preparations were not complete until the end of June. But again the wind was contrary, and for three weeks more they waited impatiently. All this while the balloon remained inflated, and by the long delay must have lost a considerable amount of its buoyancy. At last the wind changed, and though it was not exactly in the direction they wished, being a little west of south, instead of due south, AndrÉe felt he could wait no longer, and at half-past two in the afternoon of July 11th set sail, with his two friends, on his daring voyage.

What followed is soon told. Eleven days later one of the carrier pigeons taken by AndrÉe in his balloon was picked up by a fishing-boat off Spitzbergen. Fastened to it was the following message:—“July 13th, 12.30 P.M. 82° 2´ north lat., 15° 5´ east long. Good journey eastward. All goes well on board.—AndrÉe.”

This was the latest news ever heard of the ill-fated voyagers. Later on two of AndrÉe’s buoys, thrown out from the balloon, were found; but the messages these contained were dated on the evening of July 11th, only a few hours after the start. If the date of the first found message can be relied on, it would seem that after forty-eight hours AndrÉe’s balloon was still sailing well, and he had already accomplished the longest voyage aloft ever made.

Of his subsequent fate, and that of his companions, nothing is known. Search expeditions have failed to find any trace of them or of the balloon, and the many rumours received have been proved to be false. There can be no possible reason to doubt that these brave men perished in their daring attempt, and that their bones lie in the Arctic Sea or in the waste of ice and snow that surrounds the Pole.