462 PKOCEEDINGS OE THE GEOLOGICAL SOCIETY. [May 16, 



ful branch which terminates in the snowy mountains of Santa Marta, 

 enters the territory of Venezuela by the mountainous region of 

 Merida, which comprises elevations of over 14,000 feet. On ap- 

 proaching the coast, under the tenth parallel, the direction changes 

 to east, and so continues for 8 degrees, forming the southern boun- 

 dary of the Caribbean Sea, and terminating at the eastern extremity 

 of Trinidad. 



The observations on which this notice is founded only extend to 

 that portion of the Republic north of the 8th degree (corresponding 

 for a considerable distance with the position of the Orinoco) and east 

 of the 69th meridian, including, consequently, merely that section of 

 the Cordillera last enumerated, and adjacent to the sea (PL XXI.). 



In this distance the mountain series is twice interrupted : first by 

 the great indentation of the coast in the province of Barcelona, 

 dividing it into an eastern and western range ; and secondly, by the 

 Bocas or exit of the Gulf of Paria, which separates the third or insular 

 portion. 



The most ancient rocks the existence of which has been esta- 

 blished comprise a series of micaceous and siliceous schists, the 

 former especially presenting a great miiltiplicity of aspect, the mica 

 passing from silvery white to the darkest shades, and from an 

 extreme abundance to an almost entire suppression ; secondly, of 

 sandstones, in which the grains are coarse and accompanied with 

 flakes of mica, or fine and free from the latter mineral ; thirdly, of 

 shales, occasionally ferruginous, sometimes micaceous, and often car- 

 bonaceous. (See Sections, PI. XXI.) 



These various rocks seem to have experienced a segregation or 

 concentration of part of the siliceous material originally disseminated 

 throughout the strata, since the silica occurs in layers — in lenti- 

 cular or nodular forms, usually of great irregularity, but with a con- 

 stant tendency to occupy the directions of bedding and foliation. 

 The thickness of these quartzose masses (often only equalling the 

 slightest film) may attain from 4 to 6 feet of thickness, evidencing 

 the magnitude of the scale on which this process has operated. 



White or blue limestones, generally crystalline, more rarely com- 

 pact, are also members of the same series. By the association of 

 argillaceous matter and mica, they become calciferous schists. The 

 thickness of the limestones varies from a single inch to hundreds of 

 feet ; but the more massive beds are probably restricted to Trinidad, 

 as they were not observed on the mainland. 



A much rarer mineral aggregate, consisting of a base of smaragdite 

 with crystals of garnet (and consequently a species of eklogite), occurs 

 near Caracas and at Cambure, JN".W. of Porto Cabello. It is distinctly 

 stratified, and by the association of mica (scarcely ever entirely sup- 

 pressed) passes into granatiferous schist. 



An important variation in the nature of the series arises from the 

 presence of gneiss, which prevails especially at the Point of Paria (the 

 Scylla of Caracas) and between the lake of Valencia and the coast. 

 It is difficult to establish any relations of age or sequence with the 

 schists. The circumstances are rather those of alternation — a number 



