so evident a vocation, or did ours, at least, exercise a greater influence.
So unjust is the accusation that contemporary science is split up into details, that we have to go back to Newton's time to find an example of an enlargement of our theoretical conceptions, like that which was effected by the enunciation of the doctrines of the persistence of energy and motion, and of the mechanical theory of heat. As, at the former time, the fall of bodies, the motion of the stars, the refraction of light, capillarity, the ebb and flow of the tides, were recognized to be expressions of the same properties of matter, so now, through the labors of our generation of investigators, the same principle has been made to include the totality of the phenomena accessible to experiment, methodical observation, and calculation; mechanics, acoustics, optics, the Proteus electricity, heat, and the elastic phenomena of the gases and steam. This principle is not merely, like universal gravity, an experimental proposition; it conforms to the ultimate fundamental condition of our intellect. Hence its value as an aid to invention; therefore it extends far beyond the limit of its strict verification. It permits us to weigh the ether and measure the atoms. The circulation of the waters over the earth, kept up by the force of the sun's light, falls under it as well as the circulation, similarly maintained, of matter through plants and animals. Forward and backward along the "corridors of time," as the Royal Astronomer of Ireland recently expressed himself in a sharp metaphor, it leads the way, and answers that very practical question for the thinker about the beginning and end of the world, with a reservation of the limits of error, as if we were dealing with measurements in the laboratory. The same wizard's-formula lends itself to practical instruction in the ordinary sense, and shows the machinist how he may reach a desired result in the shape of mechanical force, the electrical current, or light, with the smallest quantity of coal. Inorganic and organic chemistry, separated from the beginning, now find an all-ruling principle in the quantivalence of atoms.
As mechanics and physics discovered their guiding star in the persistence of energy, and chemistry in the theory of equivalents, so is the sphere of life composed by the theory of descent into a picture which brings within a single frame the immense abundance of forms of the present with the invisible traces of the most remote past. The ban of the Cuvierian theory, to which Johann Müller opposed himself, is broken. Instead of the lifeless system of the older schools, that Darwinian tree, in whose evergreen crown man himself is only a branch, waves before us. As zoölogical gardens and stations are to 1 collections of animals, stuffed or preserved in alcohol, as botanical gardens to herbariums, so is the new knowledge of plants and animals, biology, to the older science. A development-history, as it were, of the transition of individual types from one into another, it leads back