GEOGEAPHICAL EELATIONS. 



Influence of External Conditions on Life — Their Influence on 

 Civilisation — Variation through Physical SuiToundings — 

 Power of Locality on Mental Characteristics — External 

 Conditions merely Co-factors in the Law of Variation — 

 Our Seamd Proposition. 



On surveying tlie surface of the globe — whether the 

 land or waters — ^we perceive that plants and animals 

 are not universally or indiscriminately dispersed, but 

 that certain groups are restricted to certain areas, and 

 that the range of some groups is more extensive than 

 that of others. In this distribution, climate, food, 

 geological changes of sea and land, and other physical 

 conditions, are the main factors ; for as soon as any 

 important alteration is made on these conditions, a 

 corresponding change takes place in the distribution 

 of the vital organisms. And not a change in the 

 distribution merely, but often a modification of the 

 plants and animals themselves, by which they adapt 

 themselves to their new conditions — thriving and 

 spreading, or declining and dying out, according to 

 the power of adaptability with which they are en- 



