The name of materialist, still borne to-day by certain people who see no farther than the ordinary appearances of things, could only be considered by the thinker as an outworn expression without meaning. The visible universe is not at all what it appears to be to our senses: it is the invisible universe which constitutes the essence and basis of creation. In fact, this visible universe is composed of invisible atoms which are not in contact; it hangs in the void, and the forces which control it are themselves invisible and immaterial. You may look for matter, but you will not find it; it is a mirage which recedes as we advance towards it; it is a spectre which disappears whenever we seem to seize it. It is not the same with force, the dynamic element; it is invisible and imponderable force that we find in the last analysis and which represents the basis, the support, and the very essence of the universe. In the deep and silent night everything moves driven by the breath of God. In these hours of calm reflection, do we not hear the voices of the infinite? Night is the normal condition of empty space, and we only have day during a half-rotation of the Earth because we dwell in the immediate neighbourhood of a star. Night fills all; but it is not darkness; it is the soft light shed by millions of stars. We can thus better appreciate how everything is in vibration. The movements of every atom on earth and in the heavens are the mathematical result of all the ethereal undulations which arrive in time from the abysses of infinite space. The moon attracts the Earth, the Earth attracts her sister-planets, these beckon and call her, the stars attract the Sun; and, like those motes of dust which one sees oscillating and vibrating in a beam of light, so also glide, turn, circulate, fly, vibrate, and palpitate all the worlds and all the universes, out to infinity, amidst limitless and bottomless space. A geometrician has dared to say that by stretching out his hand he could disturb the Moon in its course. This is a vivid expression of the extreme mobility of things intended to show that the feeblest displacement of the centre of gravity has a far-reaching effect. When the Moon passes over our heads it raises the whole Earth, displaces the waters of the ocean, and makes every one of us weigh 18 milligrammes less than when it is on the horizon. When Venus passes at 25 million miles from here or when Jupiter passes at 375 million miles, both displace our whole planet from its normal position.