EARTH SCIENCES IN NINETEENTH CENTURY 675 



learned to borrow and lend. The evolution of the earth and the 

 evolution of organic forms are doctrines that have reinforced each 

 other; the full meaning of both is gained only when one is seen to 

 furnish the inorganic environment, and the other to exemplify the 

 organic response. Without question, the interaction here discovered 

 in the working of two great processes is the most notable discovery of 

 the past century, not the less glorious because we share it with 

 other sciences. For if they have to do with the players, we have 

 to do with the scenery and the properties for the all-world stage, 

 where the success of the players has been conditioned by our setting 

 since the play began. In the universal habit of respiration as a means 

 of gaining the energy by which all plants and animals do their life- 

 work, we see a successful response to the presence of free oxygen, 

 mixed in the air or dissolved in the waters, and hence we infer that 

 free oxygen has been present in atmosphere and oceans, at least as 

 long as life has existed on the earth. In the development of stem 

 and root, of dorsal and ventral parts, we perceive the everlasting 

 persistence of gravity ; to fail in the recognition -of this elementary 

 example of interaction between life and environment would be on a 

 par with neglect of the earth's rotation because the evidence of it is 

 found in the commonplace consequences of sunrise and sunset. 



The races of mankind, so inappropriately treated as a chapter of 

 physical geography in many of our text-books, but really the prime 

 factor of poUtical geography, are obviously determined by the larger 

 features of the lands; just as the development of the higher organic 

 forms has been determined not on the monotonous ocean floors but 

 on the lands, where variety has really been the very spice of life. 



If we turn to history — not simply to the politics of the past, but 

 to the real history of human thought and action — the progress of our 

 own science furnishes innumerable examples of response to environing 

 opportunity : how natural that the later geological series should have 

 been first deciphered in England, where it is so well displayed; that 

 the study of earthquakes and the invention of seismographs thrive in 

 Italy and Japan; and that geomorphy advanced rapidly in our arid 

 West through the study of the nude, just as sculpture flourished in 

 Greece. 



It is but the commonplace of economics to show the large depend- 



