l8o THE ANDES RANGE CHECKING FOREST GROWTHS. 



rapid growth in the equatorial forests would, in a 

 very short time, blot out all trace of a former path. 

 Among the galleries formed under the heavier timber, 

 sometimes bearing a close resemblance to the aisle of 

 a great cathedral, the shade is, however, so deep that 

 vegetation proceeds at a very much slower rate, and 

 the ground in these places is often bare. In these 

 portions of the forest therefore, marks might remain 

 visible for a considerable time. 



The size of the South American forests is greatly 

 curtailed to the westward by the lofty snow-clad 

 range of the Andes, whose cold altitudes cause the 

 condensation of the aqueous vapour, with which 

 the atmosphere is charged, to take place upon their 

 eastern slopes, where it falls in copious rains, as the 

 enormous river systems upon that side sufficiently 

 attest. The wind then descends upon their western 

 slopes, as dry air; with the result that might have 

 been anticipated, namely, that (except at points where 

 the incessant rains prevail, in Ecuador and New Gra- 

 nada) the heavy forest disappears, and a stunted bush, 

 or arid plains, take its place, affording (if that were 

 needed) another proof of how entirely these forests 

 depend for their existence upon a moist atmosphere and 

 damp soil; combined, of course, with tropical heat. 



The remarkable difference of the climates to the east- 

 ward and westward of the Cordilleras, has always excited 

 the astonishment of beholders; for surely nothing can 

 be more striking than the intensely damp rainy climate 

 and exuberant vegetation on one side, and the sterile, 

 arid country, perishing for want of water, on the other. 

 Generally, however, this has been set down to some 

 freak of Nature. But Nature is not given to cause- 



