372 Professor Fournet's Besearches on the 



rock, rising only a few centimetres above the rest of the plain. 

 We may next remark, that, for the deep Gulf of Mexico, 

 placed between 10° and 30° N., we find substituted, in the op- 

 posite hemisphere, the broad enlargement and the mountains 

 of Brazil ; that the emaciation of form towards the South 

 Pole is the substitute for the great transversal extent in North 

 America ; and, lastly, we may notice, as another character of 

 want of symmetry, the arrangement of the royal Cordillera of 

 snows. It approaches so near to the Pacific Ocean, that the 

 space on the western side is scarcely worthy of the name of 

 plains. For its fantastic configuration in South America, there 

 is substituted a uniform plateau in Mexico ; the chief routes 

 there attain altitudes greater than the height of Mont Blanc ; 

 populous towns there exist at the level of the Col du Geant 

 and of Mont St Bernard ; and, lastly, the principal summits 

 rise above the whole to a height of from 3000 to 6500 feet ; 

 so that, a priori^ these immense heights, with their' elongatioA 

 from north to south, would seem to have caused to turn, at a 

 right angle, the meteorological system, which, in Africa, cor- 

 responds with the direction of the equator. It thus becomes 

 a matter of high interest to examine the disturbances which 

 such a discordance can produce in the regularity of the great 

 atmospheric phenomena, and to ascertain in what degree the 

 effects of pure and simple solar action are modified by orO' 

 graphical circumstances. If we still find some trace of sym- 

 metry in the position of the deserts, the influence of a very 

 energetic cause must be recognised in this trace, since it must 

 have subsisted in the midst of so many causes of anomalies ; 

 and it will thus furnish us with the best proof of the law 

 whose existence we are endeavouring to establish. 



In the latitude of the Sahara, on the coast of the great 

 ocean, the low lands of Old California are destitute of rain ; 

 the mountains which constitute the ridge of this peninsula 

 alone receive a small quantity, and the vegetation is there as 

 poor as the water is rare ; so that, in this respect, the resem- 

 blance between that portion of America and the correspond- 

 ing region of Africa could not be more complete. Neverthe- 

 less, some special phenomena seem to characterise these lati- 

 tudes; for the atmosphere, almost constantly clear, i^ always 



