220 CATARACTS OF THE ORINOCO. 



once filled the whole of this now dry gulf or bay. Probably 

 the waters formed a wide lake as long as the northern dike 

 was able to withstand their pressure. When it gave way, 

 the prairie now inhabited by the Guareke Indians must 

 have been the first part which appeared above the waters ; 

 which may subsequently, perhaps, have long continued to 

 surround the rocks of Keri and Oco, which rising like moun- 

 tain fortresses from the ancient bed of the river, present a 

 picturesque aspect. As the waters gradually diminished 

 they withdrew altogether to the foot of the eastern hills, 

 where the river now flows. 



This conjecture is confirmed by several circumstances. 

 The Orinoco, like the Nile near Philse and Syene, has the 

 property of imparting a black colour to the reddish white 

 masses of granite which it has bathed for thousands of years. 

 As far as the waters reach, one may remark on the rocky 

 shore the leaden-coloured coating described in page 189 : its 

 presence, and the hollows before mentioned, mark the ancient 

 height of the waters of the Orinoco. 



In the rock of Keri, in the islands of the Cataracts, in the 

 gneiss hills of Cumadaminari above the island of Tomo, and 

 lastly at the mouth of the Jao, we trace these black-coloured 

 hollows at elevations of 150 to 180 (160 to 192 English) 

 feet above the present height of the river. Their existence 

 teaches us a fact of which we may also observe indications 

 in the river beds of Europe ; viz. that the streams whose 

 magnitude now excites our astonishment are only the feeble 

 remains of the immense masses of water belonging to an 

 earlier age of the world. 



These simple remarks and inferences have not escaped 



