THE SCIENCE OF THE PRESENT PERIOD. 23 



so evident a vocation, or did ours, at least, exercise a greater in- 

 fluence. 



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 persist- 

 ence 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 rec- 

 ognized to be expressions of the same properties of matter, so now, 

 through the labors of our generation of investigators, the same prin- 

 ciple has been made to include the totality of the phenomena accessi- 

 ble to experiment, methodical observation, and calculation ; mechanics, 

 acoustics, optics, the Proteus electricity, heat, and the elastic phe- 

 nomena of the gases and steam. This principle is not merely, like uni- 

 versal gravity, an experimental proposition ; it conforms to the ulti- 

 mate 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 main- 

 tained, 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 begin- 

 ning 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 quantiva- 

 lence of atoms. 



As mechanics and physics discovered their guiding star in the per- 

 sistence 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 Miiller opposed him- 

 self, 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 zoological gardens and stations are to 1 

 collections of animals, stuffed or preserved in alcohol, as botanical gar- 

 dens 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 



