Page:The System of Nature.djvu/40



Every thing in the universe is in motion: the essence of matter is to act: if we consider its parts, attentively, we shall discover there is not a particle that enjoys absolute repose. Those which appear to us to be without motion, are, in fact, only in relative or apparent rest; they experience such an imperceptible motion, and expose it so little on their surfaces, that we cannot perceive the changes they undergo. All that appears to us to be at rest, does not, however, remain one instant in the same state. All beings are continually breeding, increasing, decreasing, or dispersing, with more or less dullness or rapidity. The insect called EPHEMERON, is produced and perishes in the same day; of consequence, it experiences the greatest changes of its being very rapidly, in our eyes. Those combinations which form the most solid bodies, which appear to enjoy the most perfect repose, are nevertheless decomposed, and dissolved in the course of time. The hardest stones, by degrees, give way to the contact of air. A mass of iron, which time, and the action of the atmosphere, has gnawed into rust, must have been in motion, from the moment of its formation, in the bowels of the earth, until the instant we behold it in this state of dissolution.

Natural philosophers, for the most part, seem not to have sufficiently reflected on what they call the nisus; that is to say, the incessant efforts one body is making on another, but which, notwithstanding appear, to our superficial observation, to enjoy the most perfect repose. A stone of five hundred weight seems to rest quiet on the earth, nevertheless, it never ceases for an instant, to press with force upon the earth, which resists or repulses it in its turn. Will