OCR Text |
Show 50 S'rEPPES 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 correct, 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 ? (5) p. 26.-" 'l'he Llanos and Pampas of South Ame1·ica, and the Prai1·ies of the Missrnvri." 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 J~ong, the excellent writings of his companion Edwin James, and more especially by the comprehensive observations of Captain Fremont. These, and all other recent accounts, now place in a clear light what, in my work on New Spain, I could only put forward as co~jecture, 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 bills approach the rivers Itenes and Guapore, and the mountains of Aguapehi (to the south of Villabella) approach the lofty Andes of Cocbabamba and Santa Cruz de la Sierra. |