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CHAPTER XYJII. 



PRELIMINARY. 



In examining the outer crust of the earth, endeavour- 

 ing to discover signs of movement, and the nature 

 and causes of the movements which take place, 

 suppose that, after traversing the mountains and 

 plains of Europe, you at length set oiF to look at the 

 most extensive of all mountain ridges, which is that 

 which extends almost from pole to pole along the 

 western coasts of North and South America. You 

 traverse the pampas, where the land is, for the most 

 part, slightly undulated, so that in riding over it the 

 horizon is constantly changing, and the eye is ever 

 on the alert, as objects appear or vanish in the 

 distance. After passing San-Luiz you traverse a 

 series of undulations which give to the country the 

 appearance of a succession of huge ocean rollers 

 pressing forward in parallel lines towards the moun- 

 tains. You cannot fail to be struck with the peculi- 

 arity of the scene. They are a series of undulations 

 upon a much greater undulation, for the land falls 

 again before reaching the mountains. When yet 

 two hundred miles east of that mountain range, you 

 may catch sight of it as its snow-covered peaks fling 



