12 



The breccia, or agglomerate of the seacoast, 

 which we have just described, has a white tint, 

 and lies immediately on the calcareous forma- 

 tion of Cumanacoa, which is of a blueish gray. 

 These two rocks form a contrast no less strik- 

 ing than the molasse (bur-stone) of the Pays de 

 Vaud, with the calcareous limestone of the 

 Jura *. It must be observed, that, by the con- 

 tact of the two formations lying upon each 

 other, the beds of the limestone of Cumanacoa, 

 which I consider as an Alpine limestone, are 

 always largely mixed with clay and marl. Ly- 

 ing like the mica-slate of Araya north-east and 

 south-west, they are inclined, near Punta Del- 

 gada, under an angle of 60 degrees to the south- 

 east. 



We traversed the forest by a narrow path, 

 and went along a rivulet, which rolls foaming 

 over a bed of rocks. We observed, that the 

 vegetation was every where more brilliant, 

 where the Alpine limestone is covered by a 

 quartzose sandstone without petrifactions, and 

 very different from the breccia of the seacoast. 

 The cause of this phenomenon depends proba- 

 bly not so much on the nature of the ground, 

 as on the greater humidity of the soil. The 

 quartzose sandstone contains thin strata of a 



* For example, near Aaraw, Boudry, and Porentrui in 

 Switzerland. 



