613 



II. FORMATION OF CLAYEY-SLATE (THONSCHIEFER) 

 OF MALPASSO. 



If, in the sketch of the formations of Venezue- 

 la, I had followed the received division into pri- 

 mitive, intermediary, secondary, and tertiary 

 soils, I might be doubtful what place the last 

 layer of micaslate should occupy in the penin- 

 sula of Araya. This layer, in the ravine (Aroyo) 

 of Robalo, passes insensibly in a carbu rated and 

 shining slate, into a real ampelite. The direc- 

 tion and inclination of the strata remain the 

 same, and the thonschiefer, which takes the 

 aspect of a transition-rock y is but a modification 

 of the primitive micaslate of Maniquarez, con- 

 taining garnets, cyanite, and rutile titanite 

 (Vol. vi, p. 101, 102). These insensible passages 

 from primitive, to transition soil, by clayey 

 slate that becomes carburated, at the same 

 time that it presents a concordant position with 

 micaslate and gneiss, have also been observed 

 several times in Europe * by celebrated geog- 

 nosts. The existence of an independent for- 

 mation of primitive slate (urthonschiefer), may 

 even be doubted, that is, of a formation which 



* See the excellent work of M. de Oeynhauserij Vermch 

 eiuer geogn. Beschreib. von ObeTschlesien, 1822., p. 57, 62^ 

 415. 



