For ages the men who studied nature looked upon it as little changed since it left its Maker’s hand. Of infinite stimulus was the perception that it is a drama, not a tableau, which spreads itself before the eye. Speedily and with incomparable instruction it was traced how every actor in that drama had been molded by the part it had played in maintaining itself upon the stage of life. Every rival, parasite or foe, every stress of climate, was studied in its influence on food or frame, while the ever-threatened doom for irresponsiveness was the extinction which befell countless forms once masters of the earth. No hue of scale or feather, no barb or tusk, no curve of beak or note of song but served a purpose in the plot or advanced the action in some conflict to the death. When Darwin was confronted in plant or beast by an organ or a habit which puzzled him, he was wont to ask, What use can this have had? And seldom was the question asked in vain. He laid great stress on the directive worth of a well-considered theory. He tells us, “I am a firm believer that without speculation there is no good and original observation.” In a letter he remarks, “It is an old and firm conviction of mine that the naturalists who accumulate facts and make many partial generalizations are the _real_ benefactors of science. Those who merely accumulate facts I cannot very much respect.”
In rising from facts to explanations a weighty debt is due to modern aids to eyes and hands. To men who knew only what direct vision could tell them in a single life-time, it was but natural to repeat:--“The thing that hath been, is that which shall be; and that which is done, is that which shall be done; and there is no new thing under the sun.” But we of to-day are in different case. The astronomer, joining camera to telescope, lengthens the diameter of the known universe a thousand-fold; he discovers system after system in stages of life such as our sun and its attendant orbs have passed through in ages so remote as to refuse computation. And many types of nebulae and stars are now studied which were never so much as imagined until they revealed themselves upon the photographic plate. Meanwhile the geologist, examining the closely welded ribs of our globe, comparing the birds, beasts and men of to-day with their earliest known ancestry, believes that the earth has been a scene of life for a million centuries or more. As we restore one act after another in this great cosmical drama, we are able to forecast those which may next appear. Because the whole scheme of things from centre to rim pulses in one ethereal ocean, every actor has interplay with every other, so that the sweep of events discloses a unity all the more intimate the more closely it is studied. At this hour physicists and chemists, with electricity their new servant at command, are gathering proof that what have long been called “elements,” are probably one substance, variously assembled, moving at speeds and in paths infinitely diverse, repeating in little the mighty swings of suns and planets. Throughout these researches a constant spur is the thought that here may be traced such processes of development as have been laid bare in every other province of nature. From circumference to centre, evolution is the master key of each keen questioner.