INTRODUCTION. 21 



the influences of surrounding nature. But before 

 we proceed to offer a few remarks on the origin and 

 progress of zoological science, it seems expedient to 

 mark the subjects to which the attention of the na- 

 turalist is directed. 



If we cast our eyes around, and survey, in a com- 

 prehensive manner, the objects which exhibit them- 

 selves to our view, we may form some idea of the 

 occupations of those individuals who devote them- 

 selves to the examination of nature. The surface of 

 the globe presents in part a vast expanse of water 

 bounded by the sinuosities of the shores, and in part 

 an undulating succession of plains and mountains. 

 It is enveloped with an aerial fluid, which extends 

 to a considerable height, sometimes transparent, and 

 sometimes obscured with masses of floating vapour. 



The land is diversified by slopes of every degree 

 of inclination, — extensive plains, depressions and 

 hollows, ridges and protuberances of various forms ; 

 the highest, however, bearing a very insignificant 

 proportion to the earth's diameter. The waters, 

 which cover more than two-thirds of the globe, se- 

 parate the land into unequal portions, dividing it 

 into continents and islands. Tracts of elevated 

 ground traverse these in various directions, constitut- 

 ing the elongated mountain-groups named chains ; 

 which, being intersected by valleys and containing 

 the sources of numberless streams, slope towards the 

 adjacent countries. Other portions of the surface 

 consist of irregularly- grouped eminences, of infe- 

 rior height, interspersed with corresponding valleys. 

 Elevated platforms are sometimes met with, and 

 the plains and slopes are not unfrequently diversi- 

 fied with hills. The depressed parts of mountainous 



