In a period so tumultuous as was this quarter-century, one could scarce expect that the world would make much progress in science. Men were too intent on sterner things. There was, however, just before the beginning of the French Revolution, one event which to a future generation may seem more important even than to us. Aërial navigation began. The first successful balloon ascension was made by the Montgolfier brothers, and the sport became for a while a Parisian fad.[19] Still more noteworthy was the employment of vaccination as a preventive against smallpox. The system was introduced in England by Jenner in 1798, and its use spread rapidly over Europe. More recently it has been employed against other diseases as well, and the resultant increase in the general health of mankind is beyond computation.[20] FORMATION OF THE UNITED STATES Meanwhile America, the source or at least the partial source of all this republican tumult, was having difficulties of her own. The peace after Yorktown left her exhausted. The Articles of Confederation which had sufficed to hold the colonies together under the stress of their great necessity, had proven insufficient to give any real unity. Each little colony was jealous of its own power as an independent State: and for a time it seemed as if they must disband, that America must become like Europe, divided into a collection of separate ever-jarring States, devastated by constant wars. That this was not our own country's fate, we owe to Washington. Our saviour in war, he became also our saviour in peace. After watching through some years of this disorganization, he emerged from the peaceful retirement of his country home, to urge that some means be taken to form a more perfect union. It was largely through his instrumentality that the convention of 1787 was called; and he presided over its labors. Again and again it seemed as if the convention would disband in anarchy. The antagonisms between the various delegates appeared irreconcilable. But always there was Washington to control the flaming passions, to insist upon moderation, upon union. And in the end that convention drew up the Constitution of the United States.[21] Even then there remained the task of persuading each State to accept the Constitution; and this also would have been impossible had not all men looked to Washington to act as president of the new republic, to do justice between its differing sections. Relying equally on his wisdom, his caution, and his incorruptibility, the States intrusted to him a power they would have conferred upon no other. Two years were occupied in arranging matters, and then, in 1789, the date so memorable to France as well, the new government was organized, Washington was inaugurated as President, and the United States began its stupendous career as a single nation.[22]