Such a problem is that of flying through the air. The birds have solved it long ago, but even a few yearn ago it was taken for granted that no machine or engine could be built which would lift its own weight into the upper air. But within the last year the problem of human flight has been solved completely, and probably in a few years’ time the flying machine will be seen by nearly everybody every day. This achievement means an entirely new development of civilisation. We are fortunate to live in the time of an invention which is more important than the steam-engine or the steam-ship, and will do more to bring people together than the telephone or the telegraph. We are doubly fortunate in being able to watch from day to day the manner in which the various difficulties of flying are overcome one by one. Instead of reading of great discoverers of far-off times, we can read about the triumphs of the great men of our own time. We can follow and admire the work of the heroes of science of to-day. The first instrument which enabled man to rise into the air like a bird was the balloon. Nobody knows when the first balloon was sent up. But it is reported that at Pekin, the capital of China, a balloon was sent up at the coronation of the Emperor of China so long ago as the year 1306. In the year 1709, a priest of Lisbon is reported to have ascended into the air in a balloon filled with hot air, but the first authenic account we have of such an event dates from the year 1783. Several years before that, Cavendish in England had found that hydrogen is fourteen times lighter than air, and that it therefore ascends through air. This was proved by filling a soap bubble with hydrogen instead of with air. It floated quickly up to the ceiling and then burst. This experiment set many people thinking about the possibility of getting things lifted up into the air by gas. Two of these people were brothers of the name of Montgolfier, who owned a paper factory in France. One day they made a great bag of paper and held it over the fire, thinking that the smoke from the fire would raise the bag into the air. But the paper was too heavy, and the balloon did not rise.