A few days later Pasteur might have been seen squatting before his oven, handling his rows of flasks lovingly, laughing his triumph with one of those extremely rare laughs of his--he only laughed when he found out he was right. He put down tiny scrawls in his notebook, and then crawled out of his cubby-hole to tell his assistants: “Nine out of ten of the bottles we opened in the cellar of the Observatory are perfectly clear--not a single germ got into them. All the bottles we opened in the yard are cloudy--swarming with living creatures. It’s the _air_ that sucks them into the yeast soup--it’s the dust of the air they come in with!” He gathered up the rest of the bottles and hurried to the train--it was the time of the summer vacation when other professors were resting--and he went to his old home in the Jura mountains and climbed the hill of Poupet and opened twenty bottles there. He went to Switzerland and perilously let the air hiss into twenty flasks on the slopes of Mont Blanc; and found, as he had hoped, that the higher he went, the fewer were the flasks of yeast soup that became cloudy with swarms of microbes. “That is as it ought to be,” he cried, “the higher and clearer the air, the less dust--and the fewer the microbes that always stick to particles of the dust.” He came back proudly to Paris and told the Academy--with proofs that would astonish everybody!--that it was now sure that air alone could never cause living things to rise in yeast soup. “Here are germs, right beside them there are none, a little further on there are different ones ... and here where the air is perfectly calm there are none at all,” he cried. Then once more he set a new stage for possible magnificent exploits: “I would have liked to have gone up in a balloon to open my bottles still higher up!” But he didn’t go up in that balloon, for his hearers were already sufficiently astonished. Already they considered him to be more than a man of science; he became for them a composer of epic searchings, a Ulysses of microbe hunters--the first adventurer of that heroic age to which you will soon come in this story.