In the year 1782 two young Frenchmen might have been seen one winter night sitting over their cottage fire, performing the curious experiment of filling paper bags with smoke, and letting them rise up towards the ceiling.These young men were brothers, named Stephen and Joseph Montgolfier, and their experiments resulted in the invention of the balloon.
The brothers, like all inventors, seem to have had enquiring minds.They were for ever asking the why and the wherefore of things."Why does smoke rise?" they asked."Is there not some strange power in the atmosphere which makes the smoke from chimneys and elsewhere rise in opposition to the force of gravity? If so, cannot we discover this power, and apply it to the service of mankind?"We may imagine that such questions were in the minds of those two French paper-makers, just as similar questions were in the mind of James Watt when he was discovering the power of steam.But one of the most important attributes of an inventor is an infinite capacity for taking pains, together with great patience.
And so we find the two brothers employing their leisure in what to us would, be a childish pastime, the making of paper balloons.The story tells us that their room was filled with smoke, which issued from the windows as though the house were on fire.A neighbour, thinking such was the case, rushed in, but, on being assured that nothing serious was wrong, stayed to watch the tiny balloons rise a little way from the thin tray which contained the fire that made the smoke with which the bags were filled.The experiments were not altogether successful, however, for the bags rarely rose more than a foot or so from the tray.The neighbour suggested that they should fasten the thin tray on to the bottom of the bag, for it was thought that the bags would not ascend higher because the smoke became cool; and if the smoke were imprisoned within the bag much better results would be obtained.This was done, and, to the great joy of the brothers andtheir visitor, the bag at once rose quickly to the ceiling.
But though they could make the bags rise their great trouble was that they did not know the cause of this ascent.They thought, however, that they were on the eve of some great discovery, and, as events proved, they were not far wrong.For a time they imagined that the fire they had used generated some special gas, and if they could find out the nature of this gas, and the means of making it in large quantities, they would be able to add to their success.
Of course, in the light of modern knowledge, it seems strange that the brothers did not know that the reason the bags rose, was not because of any special gas being used, but owing to the expansion of air under the influence of heat, whereby hot air tends to rise.Every schoolboy above the age of twelve knows that hot air rises upwards in the atmosphere, and that it continues to rise until its temperature has become the same as that of the surrounding air.
The next experiment was to try their bags in the open air.Choosing a calm, fine day, they made a fire similar to that used in their first experiments, and succeeded in making the bag rise nearly 100 feet.Later on, a much larger craft was built, which was equally successful.
And now we must leave the experiments of the Montgolfiers for a moment, and turn to the discovery of hydrogen gas by Henry Cavendish, a well-known London chemist.In 1766 Cavendish proved conclusively that hydrogen gas was not more than one-seventh the weight of ordinary air.It at once occurred to Dr.Black, of Glasgow, that if a thin bag could be filled with this light gas it would rise in the air; but for various reasons his experiments did not yield results of a practical nature for several years.
