CHAPTER VIII. 



ON THE ELEVATION OF THE EASTERN COAST OF SOUTH 



AMERICA. 



Upraised Shells of La Plata — Bahia Blanca, Sand-dunes and Pumice- 

 pebbles — Step-formed Plains of Patagonia, with upraised Shells — 

 Terrace-bounded Valley of Santa Cruz, formerly a Sea- strait — Up- 

 raised Shells of Tier r a del Fuego — Length a,nd breadth of the 

 elevated area — Equability of the movements, as shown by the similar 

 heights of the plains — Slowness of the elevatory process — Mode of 

 formation of the step-formed plains — Summary — Great Shingle 

 Formation of Patagonia ; its extent, origin, and distribution — 

 Formation of sea-cliffs. 



In the following Part, which treats of the geology of 

 South America, and almost exclusively of the parts 

 southward of the Tropic of Capricorn, I have arranged 

 the chapters according to the age of the deposits, occa- 

 sionally departing from this order, for the sake of geo- 

 graphical simplicity. 



The elevation of the land within the recent period, 

 and the modifications of its surface through the action 

 of the sea (to which subjects I paid particular attention) 

 will be first discussed ; I will then pass on to the tertiary 

 deposits, and afterwards to the older rocks. Only those 

 districts and sections will be described in detail which 

 appear to me to deserve some particular attention ; and 

 I will, at the end of each chapter, give a summary of 

 the results. We will commence with the proofs of the 

 upheaval of the eastern coast of the continent, from 

 the Rio Plata southward ; and, in the next chapter, 



