268 The Absence of Trees From Prairies. [June, 



%\z g^bsence of irtjes front |rai;ries 



BY PROF. D. VAUGHAN. 



While the physical wants of a vast multitude of living beings are 

 supplied by the bountiful hand of Nature, man alone has been permitted 

 to study her works, and to derive instruction and intellectual pleasure 

 from her most distant realms. By the revelations of science, he is led to 

 the contemplation of the scenes and wonders which transpire in the 

 remote domains of celestial space ; and he beholds in the crust of the 

 earth, a vivid picture of revolutions which marked the eventful periods 

 of geological history. Even the present condition of the earth's surface 

 may reveal much curious information respecting nature's mysterious 

 operations and laws ; while, at the same time, the knowledge we obtain 

 of the changes going on around us may greatly assist in ministering to 

 our bodily wants, by supplying the necessaries or the superfluities of 

 life. Of the numerous topics which Physical Geography presents to 

 our consideration, there are few that can be studied with more profit, 

 than the health of trees in different localities, and their total absence 

 from many vast plains of very considerable fertility. 



The capability of all lands for supporting animal and vegetable life 

 depends, in a great measure, on the rains they receive ; and by a very 

 admirable contrivance of nature, the atmosphere is enabled to disj.ense 

 bountiful supplies of water to most parts of the habitable globe. By the 

 influence of solar heat, water is incessantly converted into vapor, and 

 rises from the ocean to the higher regions of the atmosphere ; by the 

 motion of the air it is transported to distant regions ; and the wind fur- 

 nishes a means of carrying on, not only the commerce of art, but the far 

 more extensive and important commerce of nature It is not to be 

 expected, however, that all lands should receive an equal portion of the 

 stores of water that float around the earth ; for though very large, the 

 supply is frequently exhausted before reaching the interior of continents. 

 Accordingly, more rain falls in islands and maritime districts, than 

 in places remote from the sea ; and the amount is much greater near the 

 equator, than in high latitudes. We may ascribe the sterility of the 



