59 



which we were led at first to mistake for those 

 bats of gigantic size so well known in the equi- 

 noctial regions. Thousands of them are seen 

 flying over the surface of the water. The In- 

 dians assured us, that these birds are of the size 

 of a fowl, with a curved beak and an owl's eye. 

 They are called cacas ; and the uniform colour 

 of their plumage, which is a brownish gray, leads 

 me to think, that they belong to the genus of the 

 caprimulgus, the species of which are so various 

 in the Cordilleras. It is impossible to catch 

 them, on account of the depth of the valley ; and 

 they can be examined only by throwing down 

 rockets to illumine the sides of the crevice. 



The height of the natural bridge of Icononzo 

 above the ocean is eight hundred and ninety- 

 three metres. A phenomenon, similar to the 

 upper bridge, of which we have just given the 

 description, exists in the mountains of Virginia, 

 in the county of Rockbridge. This Mr. Jeffer- 

 son has examined with an attention, that distin- 

 guishes all the observations of that excellent 

 naturalist *. The natural bridge of Cedar 

 Creek in Virginia is a calcareous arch of twenty- 

 seven metres at its opening ; its height above 

 the waters of the river is seventy metres. 



The earthen bridge (Rumichaca), which we 

 found on the declivity of the porphyritic moun- 



* Notes on Virginia, p. 66. 



