00 ESSAY ON CLASSIFICATION. 



of the globe, 1 exhibiting the average temperature of the 

 whole year and of every season upon land and sea ; now 

 that the average elevation of the continents above the 

 sea, and that of the most characteristic parts of their sur- 

 face, their valleys, their plains, their table-lands, their 

 mountain systems, are satisfactorily known ; now that 

 the distribution of moisture in the atmosphere, the limits 

 of the river systems, the prevailing direction of the winds, 

 the course of the currents of the ocean, are not only in- 

 vestigated but mapped down, even in school atlases ; now 

 that the geological structure of nearly all parts of the 

 globe has been determined with tolerable precision, 

 zoologists have the widest field and the most accurate 

 basis to ascertain all the relations which exist between 

 animals and the world in which they live. 



Having thus considered the physical agents with 

 reference to the share which they may have had in calling 

 organized beings into existence, and satisfied ourselves 

 that they are not the cause of their origin, it now remains 

 for us to examine more particularly these relations, as an 

 established fact, as conditions in which animals and plants 

 are placed at the time of their creation, within definite 

 limits of action and reaction between them ; for, though 

 not produced by the influence of the physical world, or- 

 ganized beings live in it, they are born in it, they grow 

 up in it, they multiply in it, they assimilate it to them- 

 selves or feed upon it, they have even a modifying in- 

 fluence upon it, within the same limits as the physical 

 world is subservient to every manifestation of their life. 

 It cannot fail, therefore, to be highly interesting and in- 

 structive to trace these connexions, even without any 



1 BERGHAUS, Physikalischer Atlas; (A. K.), Physical Atlas of Natural 

 Gotha, 1838 et seq., fol. JOHNSTON, Phenomena; Edinb., 1848, 1 vol. fol. 



