Erratic Blocks. Ill 



the flesh of the Delphinus being disliked as food, great quan- 

 tities of it are wasted which might be profitably employed in 

 this way — a more valuable application of it than for manure, 

 as formerly suggested ; and if the supply were at all regular, 

 it might enable the inhabitants to increase their stock of cows 

 in winter, and thus add much to their domestic comfort. 



Edinbukqh, 25«A June 1844. 



Report on M. Alcide UOrhignifs Memoir, entitled General 

 Considerations on the Geology of South America, By M. 

 Elie de Beaumont. 



Concluded from vol. xxxvi. p. Q>2. 



Erratic blocks. — The deposit of erratic blocks, not less mys- 

 terious than that of the loam formations, also exists in South 

 America ; but there, as in Europe, it is placed at the side of 

 the loam, and appears to be parallel to it. The Pampean loam 

 is rarely mixed with pebbles, and it is only so in the moun- 

 tains. Messrs D'Orbigny and Darwin agree in saying, that 

 there is not a single rolled pebble to be met with on the sur- 

 face of the Pampas. t It is different in Patagonia, where the 

 Pampean loam does not exist, and where the Patagonian ter- 

 tiary formation is everywhere exposed. The surface of this 

 tertiary formation appears, according to M. D'Orbigny, to have 

 been furrowed by great currents of salt water coming from the 

 west. It is those currents which, according to him, have not 

 only formed vast depressions and extensive valleys, but have 

 also every where left, at the surface of the rocks, a thin mix- 

 ture of round and small porphyritic pebbles, derived, doubt- 

 less, from the rocks by which the Cordillera is composed. 

 These porphyritic pebbles, distributed over the surface of the 

 tertiary formations of a large part of Patagonia, do not extend 

 over the Pampean loam. Their transport must, therefore, have 

 been contemporaneous with the deposit of loam, or anterior 

 to it. 



* From I'Instltut, No. 540, p. 154. 

 t Darwin's Geology of the Voyage of the Beagle ; Introduction, p. iii. 



