242 



SCIENCE 



[N. S. Vol. XXXI. No. 790 



velopment of the earth's superficial forms 

 and of the earth's inhabitants. 



The science of geography, as it is com- 

 monly understood, relates to a single geo- 

 graphic condition, that of the present. 

 There have been many others in the past. 



The present geographic condition or 

 geography is peculiarly distinguished by 

 large continents and high mountains, by 

 extremes of polar cold ; by great humidity 

 of some regions and excessive aridity of 

 others, and by corresponding diversities 

 of faunas and floras. The geography of 

 Quaternary time has been and is abnor- 

 mally developed. 



The geographies of the past have been 

 individual also; sometimes, though rarely, 

 they have exhibited extreme characters, 

 equal in diversity of conditions to the Qua- 

 ternary period ; but as a rule extremes have 

 been less pronounced and a nearer ap- 

 proach to simplicity of features has pre- 

 vailed. 



Could we at any past time have viewed 

 the earth from without with an all- 

 seeing eye, during any one epoch, we 

 should have seen a single geography, a 

 panorama. If we might have maintained 

 our vigil from age to age during all her 

 history as the globe, we would have ob- 

 served the succession of geographies, a 

 long procession. 



In that procession we would have seen 

 moving forward the great lines of evolu- 

 tion in the animate and inanimate world. 



Slowly rising in response to the work- 

 ing of internal terrestrial forces, conti- 

 nents have emerged from the waters. 

 "Wasted lay erosion they have in part been 

 submerged again. Again they have risen 

 and again sunk. The rhythm of their 

 movement, the grand rhji;hm of the sphere, 

 is timed to millions of years. 



In comparison transient as the passing 

 seasons of the year, mountain chains have 



grown under temporary though titanic 

 stresses of the crust, and have wasted under 

 the rays of the sun and drops of rain. 

 Generation after generation of ranges has 

 appeai'ed, paused, and passed; incidents 

 of the geographic procession, but integral 

 features of it, obeying in time and place 

 the law of its progress. 



Atmosphere and ocean, those fluent en- 

 velopes of the sphere, have to outward ap- 

 pearance been least changeable, but they 

 also have changed. Their currents cir- 

 cling westward against the revolving sphere 

 and returning eastward, have adjusted 

 their courses to the seas and lands. 

 Subtly too the air and waters have been 

 modified chemically as the critical constit- 

 uents of the air and the soluble salts in 

 the waters ran their changes in the labora- 

 tory of land and sea. 



All of the changes suggested are linked 

 in a chain of cause and effect, from conti- 

 nental movements to atmospheric circula- 

 tion. Finally the evolution of living 

 organisms is conditioned by them all. The 

 life impulse, tending to develop new forms, 

 has been helped or hindered by environ- 

 ment. Favored by congenial and widening 

 habitats, faunas have diversified, become 

 enriched, have spread, and attained cosmo- 

 politan range. Or restricted to narrowing 

 uncongenial districts, they have lost by ex- 

 tinction of the unadaptable elements and 

 become limited to the surviving fittest. 

 Had environment been unchanging, evolu- 

 tion would have run its course chiefly ac- 

 cording to the intrinsic influence of the 

 life-principle, but since environment has 

 ever been changing, adaptation to modified 

 external influences has played a dominant 

 role. 



The great procession of geographies, 

 which has moved down the ages, has obeyed 

 those laws of inorganic and organic change, 

 which we recognize as the principles of 



