The profound Newton did not attempt to show what the gravitative force of the universe was. He bore himself more modestly, only endeavoring to show that such a force existed, and that it accounted for all the movements of celestial bodies, even to their slightest perturbations. He frankly admitted his inability to determine what this force was, but by observations and calculations made with the greatest care, he ascertained that its action upon matter was proportional to its mass directly, and to the square of its distance inversely; and, with the requisite data and the principles of pure geometry, he demonstrated that this mysterious force--utterly inapproachable by human conception in its mystery--not only governs and controls the movements of all the mighty masses of matter rolling in space, but transmits its influence--not successively, but instantly and without diminution--to the smallest conceivable molecule on the outlying boundaries of the universe. In the same calm and comprehensive spirit, if it be possible for us to reach it, let us look upon this mysterious force called "life," not to show that it is simply a "correlate" of this or that motion (a thing utterly impossible of demonstration, if it actually exists), but to ascertain how and in what way it acts, and by what known law, if any, it is governed. In all the vast realm of Reality there is no more conclusive and palpable fact than that "life" exists--appearing wherever the bright light flashes, the loving raindrop falls, the dancing brook ripples, the sparkling streamlet murmurs, and the broad river flows to mingle with the sea. All along this bright pathway of sunlight and cool translucent wave, this wonderful principle of vitality manifests itself in all-glorious life--filling the air with balmy odors; making perennial bud, leaf and flower, speeding from sire to son, from heart to heart, from spirit to spirit, from age to age, from time into eternity.[4] For like all living principles, in this realm of Reality, it cannot die. It is immortal in its primal source, immortal all along its bright pathway, immortal as it flows onward to eternity, immortal in its return to the bosom of God. It is no postulate, no corollary, no mere hypothetical judgment; no "undiscovered correlative of motion," no "baseless fabric of a vision"--but the one grand comprehensive _Datum_ on which all the objective, as well as subjective, data of the universe rest. It is the same "spirit that moved upon the face of the depths," in that majestic Dawn of Creation when the "evening and the morning were the first day;" the same spirit that "upholds the order of the heavens;" that pervades the vast realm of Reality, that flashes in the bright sunlight, descends in the loving raindrop, ripples in the dancing brook, sparkles in the murmuring stream, and forever flows onward bearing its primal fulness to the sea.