of a storm-cloud is a continuous process in the atmosphere, or the appearance of a rash in the human patient is continuous. But the cataclysm once accomplished, a new uniformity must have supervened, and evolution proceeded from that point continuously from the simple to the more heterogeneous, in accordance with strict dynamical law. Even now the history of such evolution is as plainly to be read as the history of the growth of plants in a forest. Some of the nebulæ give evidence of being collections of the simplest primordial gases, or mixtures of such, by the simplicity of their spectral lines. Even in these, radiant energy is being set free, or we could not know of their existence. We also know that the sun and stars are tremendous laboratories for the organization of matter, where disused motions are liberated in torrents. The creation of molecules in gradually increasing complexity seems to go on by discontinuous steps or stages, in accordance with the discontinuous and discrete nature of the elemental factors; and its products at each certain stage are all duplicates, whether in this sun or that. Every increase in complexity apparently liberates motion, which, by the law of conservation, must escape as an efficient agent. With the constant escape of energy, however, solidification finally ensues, as our planet bears witness, and the mobility of the molecules practically ceases. Gases and moisture, however, remain over to supply mobile conditions, and the work goes on. At this stage new supplies of sufficient temperature from without are capable of reversing the process to a degree, restoring mobility, and introducing new modes for the play of affinities. The radiant energies of the sun supply for our planet the extraneous motion necessary to carry the complexity of the molecule higher than the simple running down of matter can do, and we have the chemistry of the carbon compounds. Aided by some discontinuous step, which we can not as yet identify or explain, vitalized functions appear. The wondrously compound molecules of the tropics are evolved, oils, starches, sugars, spices, ethers, and alkaloids—magazines of stored-up vis viva—and, by the assimilation of these, physiological phenomena in sentient beings are carried on, accompanied by the mysteries of will and consciousness, and the still more unaccountable facts of succession and heredity, which mock, if material, all efforts at conception or comprehension of matter in its ultimate essence.
The actual amount of energy stored up in the elementary molecule is not calculable, but it must be enormous. The amount of motion can not be certainly known, for we do not know whether any could have disappeared at the birth, and the mass or atomic weight of the ultimate particle can not be known by any means now in possession. The great rapidity of oscillation across the small orbit has been vividly illustrated by G. J. Stoney ("London, Edinburgh, and Dublin Philosophical Magazine," August, 1868, page 132), by the consideration (since numbers convey no idea) that they bear the same ratio of