498 THE POPULAR SCIENCE MONTHLY. 



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 irrespon- 

 siveness 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 som'e life story of conflict. 

 When Darwin was eonfronted 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 ap- 

 peared 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 back- 

 bone 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 prom- 

 ontory and coast line which has meant so much to humankind. 



