S. S. Soworth — Elevation of American Cordillera. 449 



Elsewhere again he points to other facts which prove more 

 directly the coincidence in time of the rise of the Cordilleras and the 

 deposit of the Pampas mud by the waters as the result of this 

 elevation are without doubt the numerous depressions and denuda- 

 tions which cut into the soil from east to west, and the dispersion of 

 porphyry boulders over all the Tertiary deposits of Patagonia. If 

 these denudations had been subsequent to the deposit of the Pampas 

 mud, it is evident that the porphyritio boulders with which the 

 ground is covered over round the circumference of the Pampas 

 would also have covered the Pampas deposit, whereas they cease 

 just where the Pampas mud begins, as Darwin showed when he 

 says they are found from the Straits of Magellan to the Rio Colorado. 

 We may thus look upon the elevation of the Cordilleras as the cause 

 which at the same time drove the water from West to East with 

 sufficient violence to denude the Tertiary soil in the direction of the 

 slope, and to sweep from the Andes the porphyry boulders which 

 cover all Patagonia, and we may see in the same fact the reason 

 why the vegetable soil, etc., was swept from all the Tertiary strata 

 of Patagonia to be deposited in the great reservoir of Pampas mud. 



I hold that the waters which deposited the Pampas mud were 

 salt, because all the clay deposits of the Upper Andes containing 

 bones are saline. It is so also with the Pampas mud, which shows 

 efflorescence at different points. But the best proof is the existence 

 of salt lakes dating from this period at the summit of the Cordilleras, 

 and in all the depressions caused by water in the plains of Patagonia, 

 and this perhaps accounts for the salt springs occurring in various 

 places" (D'Orbigny, vol. iii. part 3, p. 82, etc.). 



These views were shared by other inquirers. Thus in a report to 

 the French Academy on the discoveries made by Lund in Brazil, 

 we find the reporters, Brongniart, Dufrenoy, and Elie de Beaumont, 

 saj'ing, " The deposit in Brazil only differs from that of the Pampas 

 by the presence of quartz pebbles, probably derived from subjacent 

 beds ; there it is from 3 to 16 metres thick, and extends up the 

 flanks of the mountains to a height of 2000 metres." Mr. Lund 

 attributes the red loam of Brazil to a great irruption of waters 

 which covered all this part of the earth, and put an end to the 

 existence of living animals. "Whatever modifications this hypothesis 

 is destined eventually to suffer, it seems to us evident," say the 

 learned reporters, " that the extension of the Pampas mud over the 

 mountains of Brazil upsets the theory that this mud was deposited 

 tranquilly in the estuary of a great river, and this extension seems 

 very probable, since the Brazilian mountains are not the only ones 

 where it occurs." .... The area covered by the Pampas mud is 

 equal to that of France, and the deposit which contains Megatherium, 

 Megalonyx, Hoplophorus, and Mastodon, on the Parana, is 200 myria- 

 metres from Minas Geraes, where Lund found the same animals, 

 proving that the cause of their deposition operated on a great scale 

 over the continent of America, and that we must invoke, if we are 

 to explain it, some general and widespread cause. 



I have not pretended in this short paper to do more than collect 



DECADE III. — VOL. Till. — NO. X. 29 



