338 PHYSICAL GEOGRAPHY. 



of the currents of the atmosphere which has begun afar 

 off, and generally not at the surface of the earth but in the 

 higher regions, and which, bringing with it either warm or 

 cold, dry or moist, air, either renders the sky and the 

 atmosphere cloudy and thick, or serene and clear, by trans- 

 forming the towering masses of cumuli into light feathery 

 cirrous clouds. As, therefore, the inaccessibility of the 

 primary phenomena is added to the multiplicity and com- 

 plication of disturbances, it has always appeared to me that 

 meteorology must seek its foundations and its advance first 

 in the torrid zone ; in those more favoured regions where 

 the same breezes always blow, and where the ebb and flow of 

 atmospheric pressure, the course of hydro-meteors, and the 

 phenomena of electric explosions, all recur periodically. 



Having now passed through the entire circle of terrestrial 

 inorganic nature, having considered our planet in respect to 

 its form, its internal heat, its electro-magnetic charge, its 

 polar luminous effusions, the reaction of its interior on its 

 variously composed crust, and finally the phenomena of its 

 oceanic and atmospheric envelopes, the view which we have 

 essayed to trace in broad and general outlines might be re- 

 garded as complete, and would be so according to the limi- 

 tation formerly adopted in physical descriptions of the 

 globe. Bu! the plan which I have proposed to myself has 

 a more elevated aim, and I should regard the contemplation 

 of nature as deprived of its most attractive feature, were 

 it not also to include the sphere of organic life with 

 its many gradations of development. The ide| of life is 

 so intimately connected with the moving, combining, 

 forming, and decomposing forces which are incessantly in 



