chap. xv. Summary and Conclusion, 603 



of extreme violence, presents insuperable difficulties, 

 except on the admission that the masses of once lique- 

 fied rocks of the axes were repeatedly injected with 

 intervals sufficiently long for their successive cooling 

 and consolidation. Finally, if we look to the analogies 

 drawn from the changes now in progress in the earth's 

 crust, whether to the manner in which volcanic matter 

 is erupted, or to the manner in which the land is histo- 

 rically known to have risen and sunk : or again, if we 

 look to the vast amount of denudation which every part 

 of the Cordillera has obviously suffered, the changes 

 through which it has been brought into its present con- 

 dition, will appear neither to have been too slowly 

 effected, nor to have been too complicated. 



Note. — As, both in France and England, translations of a passage 

 in Prof. Ehrenberg's Memoir, often referred to in the Eleventh 

 Chapter of this volume, have appeared, implying that Prof. Ehrenberg 

 believes, from the character of the Infusoria, that the Pampean for- 

 mation was deposited by a sea-debacle rushing over the land, I may 

 state, on the authority of a letter to me, that these translations are 

 incorrect. The following is the passage in question : — ' Durch 

 Beachtung der mikroscopischen Formen hat sich nun f eststellen lassen, 

 dass die Mastodonten-Lager am La Plata und die Knochen-Lager 

 am Monte Hermoso, so wie die der Eiesen-Gurtelthiere in den 

 Diinermugeln bei Bahia Blanca, beides in Patagoniec, unveranderte 

 brakische Susswasserbildungen sind, die einst wohl sammtlich 

 zum obersten Fluthgebiethe des Meeres im tieferen Festlande 

 gehorten.' — Monatsberichte der konigl. Akad. etc., zu Berlin, vom 

 April 1845. 



