50 STEPPES AND DESERTS. 



apt to cause fevers and other illnesses. Several missionary villages 

 have been deserted or removed elsewhere in consequence of this 

 opinion, which is very widely diffused. Supposing the opinion cor- 

 rect, is such an influence of these flat rocks or laxas to be attributed 

 to a chemical action on the atmosphere, or merely to the effect of 

 increased radiation ? 



n 



( 5 ) p. 26. " The Llanos and Pampas of South America, and the 



Prairies of the Missouri" 

 The physical and geognostical views entertained respecting the 

 western part of North America have been rectified in many respects 

 by the adventurous journey of Major Long, the excellent writings 

 of his companion Edwin James, and more especially by the com- 

 prehensive observations of Captain Fremont. These, and all other 

 recent accounts, now place in a clear ligljt what, in my work on 

 New Spain, I could only put forward as conjecture, on the subject 

 of the mountain ridges and plains to the north. In the description 

 of nature as well as in historical inquiries, facts long remain isolated, 



until by laborious investigation they are brought into connection 



^ with each other. 



The east coast of the United States of North America runs from 

 south-west to north-east, in the same, direction as that followed in 

 the southern hemisphere by the Brazilian coast from the river Plate 

 to Olinda. In the two hemispheres two ranges of mountains exist 

 at a short distance from the eastern coast ; they are more nearly 

 parallel to each other than they are to the more westerly chain, 

 called in South America the Cordilleras of Peru and Chili, and in 

 North America the Rocky Mountains. The Brazilian system of 

 mountains forms an isolated group, of which the highest summits 

 (the Itacolumi and Itambe) do not rise above the height of 900 

 toises (5755 English feet). The most easterly ridges, which are 

 nearest to the Atlantic, follow a uniform direction from SSW. to 

 NNE. ; more to the west the group becomes broader, but diminishes 

 considerably in height. The Parecis hills approach the rivers Itenes 

 and Gruapore", and the mountains of Aguapehi (to the south of Vik 

 labella) approach the lofty Andes of Cochabamba and Santa Cruz 

 cle la Sierra. 



