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 443 the Central Meteorological Bureau reported, at the moment of starting, a south-east wind blowing six metres per second—twenty-one kilometres per hour—at the altitude of the Eiffel Tower.

At Monaco in the early part of 1902 I dealt so continually with the wind that I was never able to make a satisfactory estimate of my speed. Up and down the Mediterranean coast I sped, sometimes accelerated, sometimes retarded by the wind ; and so I came to look on the entire wind-problem as simply one of plus and minus as to speed and of the toughness of superposed silk and varnish with respect to pressure ; and my strongest impression of those Mediterranean flights remains that I rejoiced, laughing to see how I outsped and left behind me the steam-chaloupes and petroleum launches that ought to have accompanied me to pick me up in case I fell!

Everything I have thus far accomplished has become common-place. It is known, it has been seen, it seems natural, not unusual. But let us not forget that the commonplaces of 1902 were the impossibilities of 1898.

I said this to myself. I had tired of straining for speed to gratify the curiosity of others; and so I permitted myself to take some aerial amusement. I built my little "No. 9," in which, day after day, I hopped over the trees of the Bois, kept appointments to lunch, attended a review, and guide-roped down the Avenue des Champs Elysées to my door at the corner of the Rue Washington.

That was one kind of air-ship. Had I at that moment predicted that, within two years, I would go on aerial pleasure-cruises of a week's length, accompanied by friends whom I would lodge, feed, and keep warm, while they should sleep between the constellations and the earth, and exult through golden afternoons spent gliding over Europe, I should have heard all the old objections—and some new ones.

Why is it that no balloon has ever been able to stay much longer than twenty-four hours in the air, and that the world's record, made in a recent sensational contest, is not quite thirty-six hours?

It is because ballooning has two great enemies—condensation and dilatation. Suppose that you are at equilibrium at five hundred metres. Suddenly a little cloud masks the sun. The gas in the balloon cools and condenses, and if you do not at once