In The Region Of The Littoral Chain Of Venezuela, Where Granite Seems To Constitute An Independent Formation From 15 To

16 leagues in length, I saw no foreign or subordinate layers of gneiss, mica-slate or primitive limestone.* (* Primitive limestone,

Everywhere so common in mica-slate and gneiss, is found in the granite of the Pyrenees, at Port d'Oo, and in the mountains of Labourd.)

The Sierra Parime is one of the most extensive granitic strata existing on the globe;* but the granite, which is seen alike bare on the flanks of the mountains and in the plains by which they are joined, often passes into gneiss. (* To prove the extent of the continuity of this granitic stratum, it will suffice to observe that M. Leschenault de la Tour collected in the bars of the river Mana, in French Guiana, the same gneiss-granites (with a little amphibole) which I observed three hundred leagues more to the west, near the confluence of the Orinoco and the Guaviare.) Granite is most commonly found in its granular composition and independent formation, near Encaramada, at the strait of Baraguan, and in the vicinity of the mission of the Esmeralda. It often contains, like the granites of the Rocky Mountains (latitude 38 to 40 degrees), the Pyrenees and Southern Tyrol, amphibolic crystals,* disseminated in the mass, but without passing to syenite. (* I did not observe this mixture of amphibole in the granite of the littoral chain of Venezuela except at the summit of the Silla of Caracas.) Those modifications are observed on the banks of the Orinoco, the Cassiquiare, the Atabapo, and the Tuamini. The blocks heaped together, which are found in Europe on the ridge of granitic mountains (the Riesengebirge in Silesia, the Ochsenkopf in Franconia), are especially remarkable in the north-west part of the Sierra Parime, between Caycara, the Encaramada and Uruana, in the cataracts of the Maypures and at the mouth of the Rio Vichada. It is doubtful whether these masses, which are of cylindrical form, parallelopipedons rounded on the edge, or balls of 40 to 50 feet in diameter, are the effect of a slow decomposition, or of a violent and instantaneous upheaving. The granite of the south-eastern part of Sierra Parime sometimes passes to pegmatite,* composed of laminary felspar, enclosed in curved masses of crystalline quartz. (* Schrift-granit. It is a simple modification of the composition and texture of granite, and not a subordinate layer. It must not be confounded with the real pegmatite, generally destitute of mica, or with the geographic stones (piedras mapajas) of the Orinoco, which contain streaks of dark green mica irregularly disposed.) I saw gneiss only in subordinate layers;* (* The magnetic sands of the rivers that furrow the granitic chain of the Encaramada seem to denote the proximity of amphibolic or chloritic slate (hornblende or chloritschiefer), either in layers in the granite, or superposed on that rock.); but, between Javita, San Carlos del Rio Negro, and the Peak of Duida, the granite is traversed by numerous veins of different ages, abounding with rock-crystal, black tourmalin and pyrites. It appears that these open veins become more common on the east of the Peak of Duida, in the Sierra Pacaraina, especially between Xurumu and Rupunuri (tributaries of the Rio Branco and the Essequibo), where Hortsmann discovered, instead of diamonds* and emeralds, a mine (four) of rock-crystal. (* These legends of diamonds are very ancient on the coast of Paria. Petrus Martyr relates that, at the beginning of the sixteenth century, a Spaniard named Andres Morales bought of a young Indian of the coast of Paria admantem mire pretiosum, duos infantis digiti articulos longum, magni autem pollicis articulum aequantem crassitudine, acutum utrobique et costis octo pulchre formatis constantem. [A diamond of marvellous value, as long as two joints of an infant's finger, and as thick as one of the joints of its thumb, sharp on both sides, and of a beautiful octagonal shape.] This pretended adamas juvenis pariensis resisted the action of lime. Petrus Martyr distinguishes it from topaz by adding offenderunt et topazios in littore, [they pay no heed to topazes on the coast] that is of Paria, Saint Marta and Veragua. See Oceanica Dec. 3 lib. 4 page 53.)

(b) GNEISS predominates along the littoral Cordillera of Venezuela, with the appearance of an independent formation, in the northern chain from Cerro del Chuao, and the meridian of Choroni, as far as Cape Codera; and in the southern chain, from the meridian of Guigne to the mouth of the Rio Tuy. Cape Codera, the great mass of the Silla of Galipano, and the land between Guayra and Caracas, the table-land of Buenavista, the islands of the lake of Valencia, the mountains between Guigne, Maria Magdalena and the Cerro do Chacao are composed of gneiss;* (* I have been assured that the islands Orchila and Los Frailes are also composed of gneiss; Curacao and Bonaire are calcareous. Is the island of Oruba (in which nuggets of native gold of considerable size have been found) primitive?); yet amidst this soil of gneiss, inclosed mica-slate re-appears, often talcous in the Valle de Caurimare, and in the ancient Provincia de Los Mariches; at Cabo Blanco, west of La Guayra; near Caracas and Antimano, and above all, between the tableland of Buenavista and the valleys of Aragua, in the Montana de las Cocuyzas, and at Hacienda del Tuy. Between the limits here assigned to gneiss, as a predominant rock (longitude 68 1/2 to 70 1/2 degrees), gneiss passes sometimes to mica-slate, while the appearance of a transition to granite is only found on the summit of the Silla of Caracas.* (* The Silla is a mountain of gneiss like Adams Peak in the island of Ceylon, and of nearly the same height.) It would require a more careful examination than I was able to devote to the subject, to ascertain whether the granite of the peak of St. Gothard, and of the Silla of Caracas, really lies over mica-slate and gneiss, or if it has merely pierced those rocks, rising in the form of needles or domes.

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