Page:Popular Science Monthly Volume 45.djvu/516

498 its every part, however diverse and remote. It is a drama, not a tableau, which the observer to-day sees spread before him; in that drama every actor has been molded by the part it has had to play to maintain itself upon the stage; every rival, every parasite, every stress of climate with all its influence on food and frame has left its impress; and the ever-threatened doom for irresponsiveness has been the extinction pronounced upon countless forms once masters of the earth. No hue of feather or scale, no barb or horn, no curve of beak or note of song but has served a purpose in the plot or advanced the action in some life story of conflict. When Darwin was confronted in plant or beast by an organ which puzzled him, he was wont to ask, What use can this have had? And rarely was the question asked in vain. In the lunar or weekly recurrent periods of many animal functions there appeared to him a lingering registry of primordial birthplaces; ancestral inhabitants of seashores washed by tides being, in alternate submergence and exposure, profoundly affected in frame and habit.

What is true of the drama of organic life is equally true of the theater in which that drama is enacted. The more thorough its exploration by the geologist, the more extended in time the range of his admissible computations, the more convincing proof does he gather that our planet has become what it is in obedience to forces such as make the world at sunset a little different from the earth that faced the dawn. The hills once called eternal he knows to be anything but changeless, for their very prominence has made them special targets for the fury of tempests, the dividing axe of frost. At the bidding of impulses as irresistible, impulses hidden in the planet's core, a mountain is lifted in a valley's place, and the threatened denudation of a continent by the work of rain and river is silently compensated. And as Prof. Sterry Hunt was accustomed to point out, in the very constitution of the rocks before they bloomed with life, there was prefigured the struggle soon to be illustrated in plant and fish and insect. Amid the wealth of mineral compounds brought to birth only the stablest could survive the ceaseless stress of impinging forces. And these forces as they swept the lifeless globe—how decisive their after influence on herb, and beast, and man! Here, lifting the backbone of a continent, which all the storms of ages should leave a backbone still; there, in mid-ocean bidding an island rise from a volcano's heart; or decreeing a Sahara, or an Australian desert even more forbidding, where only cactus of the hardiest should ever fringe its dust-blown confines. In all this ever-shifting scene of action were laid the foundations of future barrenness of crag or fertility of plain, of that rich variety of earth sculpture in promontory and coast line which has meant so much to humankind.