What was known of the Infinite prior to 1600? Nothing whatever. Nothing of the infinitely great; nothing of the infinitely little. The celebrated page of Pascal, very frequently cited upon this subject, is the frank astonishment of a humanity so old and yet so young, which begins to be aware of its prodigious ignorance, opens its eyes to the Real, and awakens between two abysses. No one forgets that in 1610 Galileo, having received from Holland a magnifying lens, constructed the telescope, elevated it in position, and saw the firmament. But it is less generally known that Swammerdam, seizing, with the instinct of genius, on the imperfect microscope, directed it to the lower world, and was the first to detect the living infinite, the world of animated atoms! These great men succeeded one another. At the epoch of the famous Italian's death (1632) was born the Hollander, the Galileo of the infinitely little (1637). An astounding revolution! The abyss of life was unfolded in its profundity with myriads upon myriads of unknown beings and fantastic organizations of which men had not even dared to dream. But the most surprising circumstance is, that the very method of the sciences underwent a total change. Hitherto men had relied upon their senses. The severest observation invoked their testimony, and they thought that no appeal could lie from their judgment. But now behold experiment and the senses themselves, rectified by a powerful auxiliary, confess that not only have they concealed from us the greater part of things, but that, in those they have laid bare, they have every moment been mistaken! Nothing is more curious than to observe the very opposite impressions produced by these two revolutions upon their authors. Galileo before the infinite of heaven, where all appeared harmonious and marvellously ordered, felt more of joy than of surprise; he announced his discoveries to Europe in a style of the greatest enthusiasm. Swammerdam, before the infinite of the microscopic world, seemed overcome with terror. He recoiled before the spectacle of Nature at war, devouring her very self. He grew perturbed; he seemed to fear that all his ideas and beliefs would be overthrown: a melancholy and singular condition, which, added to his incessant labours, shortened his days. Let us pause awhile to dwell upon this creator of science, who was also its martyr. The eminent physician Boerhaave, who, a hundred years after Swammerdam's time, published with pious care his "Bible of Nature," gave utterance to a surprising observation, which sets one a-dreaming:-- "He had an ardent imagination of impassioned melancholy, which raised him to the sublime."