616 



The fine saussurite which we saw in the Upper 

 Oroonoko in the hands of the Indians, seems 

 to indicate the existence of a soil of euphotide, 

 superposed on gneiss-granite, or the amphibolic 

 slate of the eastern part of Sierra Parime. (Vol. 

 p. 383, 384, 563, &c.) 



IV. GRANULAR AND MICACEOUS LIMESTONE OF THE 

 MORROS OF SAN JUAN. 



The Morros of San Juan rise in a soil of dio- 

 rite, like towers in ruin. They are formed of a 

 cavernous greyish green limestone, of crystalline 

 texture, mixed with some spangles cf mica, and 

 destitute of shells. We recognize in them 

 masses of hardened clay, black, fissile, charged 

 with iron, and covered with a crust, yellow 

 from decomposition, like basalts and amphibo- 

 lites. A compact limestone containing vestiges 

 of shells, is joined to this granular limestone of 

 the Morros of San Juan, which is hollow with- 

 in (Vol. iv, p. 279 ; Vol. vi, p. 583). It is pro- 

 bable that in further examining the extraordi- 

 nary soil, between Villa de Cura and Ordiz, in 

 which I could only collect specimens of rock 

 during one day, many phenomena may be dis- 

 covered analogous to those which M. Leopold 

 de Buch has lately described in South Tyrol *. 



* Tyroler Bothe vem 26 ten Julius, 1822 - } and Geognostic 

 Letter of M. de Buch to M. de Humboldt, 1823, p. 13. 



