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.