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Aeronautics

FROM very remote times men have endeavoured to find out some means of navigating the air like the birds and insects which they see daily around them. There are many fabulous stories of people who have succeeded in flying by means of artificial wings; but these stories are not more worthy of belief than the tales of fairyland, where you know that most people have the advantage of being able to fly.

The first balloon was made by the brothers Montgolfier, the sons of a paper manufacturer in the South of France. These two brothers seem to have spent their time in making scientific experiment, and in the course of these experiments they found that common air, when heated, speedily increased in bulk. We can try this for ourselves by blowing a bladder half full of air, and securely tying up the opening. When such a bladder is placed before the fire, it will speedily swell until it is quite tense, and if the heat be continued, it will presently burst with a loud report. Now it is very evident that air in this heated and expanded state is much lighter, bulk for bulk, than air at the normal temperature. Hot air therefore rises in the denser medium by which it is surrounded. You have merely to stand on a table in a gaslit room to find out this fact, for you will quickly perceive that the air at the upper part of the room is very much hotter than that below. To use this hot air for ballooning purposes, it is necessary to secure it in some very light cover, or envelope, when it will pull up this cover with it. Such an envelope constitutes a fire balloon, and it was such a balloon that was first made by the two brothers Montgolfier. For this reason that form of balloon is very often called a Montgolfier, in contradistinction to those which are filled with gas.

A fire balloon can very easily be made of tissue paper. This is the only kind of paper suitable for the purpose, for it is of extremely close texture, and is also of very light weight. The first operation is to make a pattern from which to cut the gores of the balloon. A good idea of the shape of these may be gained from cutting the peal of an orange into twelve equal parts. Each part, if properly cut, will take the form shown at A. By this analysing process we shall know that a round body can be built up of such segments. But a balloon is better made pear-shaped, and to obtain this, the pattern must be slightly modified, as at B. With regard to the size of the balloon, we should cut our coat to suit our cloth, or, rather, cut our balloon to suit our paper. Tissue paper measures about two feet six inches by twenty inches. Two sheets fastened together longways, so as to measure five feet long, will cut into two such gores, and six gores will give the right proportions for a balloon five feet high. These gores may with advantage be of two different colours, white and blue, or white and red, being perhaps the most effective combinations for the purpose. Twelve sheets of paper, six of one colour and six of the other, will therefore be sufficient to make the balloon.

The gores should all be accurately cut by the pattern; indeed, the paper is so thin that they can with a good pair of scissors be all cut with one operation. Before attempting to join them up, the gores should each be separated and folded down the centre, the folded edges being placed altogether. The two edges of the top pair of gores can now be neatly pasted together with good starch paste used warm. They are then dabbed with a clean cloth and folded back out of the way, while the next two edges are similarly treated. When all the gores are joined up in this way, the balloon can be put aside to dry. The next operation is to close in the top of the balloon, where the gores meet, with a disc of tissue paper on each side, a piece of thread being pasted in between them, the end of which should project in a loop through a hole in the upper disc so that the balloon can be conveniently held by it. The lower opening must be held open by a ring of bonnet wire, over which the edge of the paper is folded and pasted. When all is dry, the balloon is ready forinflation. The heat from a piece of burning paper held below the opening at a safe distance will cause it quickly to distend its sides, and this will give the opportunity of seeing any holes or apertures between the gores where the paste has failed to act. These must be stopped by patches of paper, and the balloon is then ready for flight.

Across the ring of wire at the bottom of the machine must be stretched a piece of fine binding wire, and in the centre of this is fastened either a piece of wool or sponge. The balloon must then be inflated as before by burning paper, and as soon as it is quite full of hot air, the paper must be held aside, while the wool or sponge is saturated with spirits of wine. This is now lighted, and presently the balloon will soar aloft and will be quickly out of sight.

The balloons made by the Montgolfiers were constructed of paper and lined with linen. The heat was obtained from burning straw which was placed in a furnace underneath the lower orifice of the balloon. A great many successful ascents were made by these means, but there were also several fatal accidents. The risks attending the use of fire balloons are very many. First there is the probability of the balloon catching fire from the furnace beneath. This difficulty can be obviated by soaking the balloon material in some chemical solution, such as tungstate of soda, which renders it uninflammable. Another great danger in the use of this form of balloon is the accumulation of unconsumed vapours, which may at any moment explode. For these and many other reasons the fire balloon has been almost entirely superseded by that which owes its rising power to hydrogen gas.

Some few years before the time of Montgolfier, an Englishman named Cavendish discovered a peculiar vapour, to which he gave the name of inflammable air. This gas has now become familiar to us, for it furnishes our houses and streets with artificial light. It was soon found that this gas was the very lightest thing known, and Dr. Black, of Edinburgh, was the first to suggest that, if a bladder were filled with it, it ought to rise in the air. A bladder was, however, too heavy to rise, and another experimenter filled soap bubbles with the gas, and found that they speedily flew upwards. With an india-rubber tube fastened to the gas-burner, a tobacco-pipe, and a little soap and water, this experiment can be easily repeated. From it was gleaned the first idea of a gas balloon, and the machine has been improved from time to time, until it has reached absolute perfection in the colossal balloon lately exhibited at Paris. This balloon could carry up a weight of twenty-two tons. It was attached to a rope which held it captive, and rose several times a day for the benefit of those who wished to see the beautiful city of Paris from a bird's point of view. This balloon unfortunately was rent to pieces during a high wind, but as the accident occurred when it was on the ground, nobody was hurt. The directions given for making a fire balloon apply to the construction of a gas balloon with one or two modifications. The opening at the lower part must be only sufficiently large to admit a pipe for inflation, and the gores must be painted over with boiled linseed oil and dried before being put together. If inflated with pure hydrogen, the gas must be made by pouring sulphuric acid and water (seven parts of acid to one of water) upon zinc-cuttings or iron waste in a stone bottle; a pipe fitted through the cork of the bottle carrying the gas evolved to the balloon. Common house gas (carburetted hydrogen) is not so light, but it does almost as well for the purpose. Moreover, the trouble of preparation with a dangerous acid is avoided. It has also the advantage of being much cheaper, the cost of filling a balloon of the size in question being about one penny.

It is thought by most people who have given attention to the subject, that the balloon will never contribute more than it has done to the conquest of the air. A great many plans for guiding it in the air have been tried and have failed. The mass of a balloon presents such an obstacle to the wind that it is quite hopeless to attempt to guide it against such a powerful adversary. If an efficient flying machine is ever made, we may be quite sure that it will not partake of the form of a balloon.