260 ANNUAL OF SCIENTIFIC DISCOVERT. 



donts of Brazil, and its gigantic sloths and armadillos, rival the 

 elephants, rhinoceros, and hippopotami, which, during the same 

 period, roamed the soil of Europe. — Geological Magazine. 



VOLCANIC EMANATIONS. 



The eruption of Vesuvius in January, 1868, confirms the obser- 

 vations of C. St. Claire Deville, on the order of succession of vol- 

 canic emanations. 1. Dry fumerolles : at the commencement of 

 the eruption the emanations are neutral, the air being very poor 

 in oxygen, and depositing almost exclusively alkaline chlorides, 

 soon covered with a thin layer of chloride or oxide of copper. 2. 

 Chlorhydrosulphurous emanations : in a few days, and in the cold- 

 est portions, chlorhydric and sulphurous acids appear, accompa- 

 nied by watery vapor ; the carbonate of ammonia, seemingly of 

 two different origins, is naturally transformed into the chlorhy- 

 drate ; in general, sulphydric and carbonic acids and carburetted 

 hydrogen have not appeared. 3. Sulphurous, and 4. Carburetted 

 emanations. Observations at Vesuvius and Etna have confirmed 

 this order of succession. 



THE GOLD FIELDS OF VENEZUELA. 



According to a paper read before the Lyceum of Natural His- 

 tory of New York, by Mr. R. P. Stevens, Venezuela is divisible 

 into three grand hydrographical basins, each of which represents 

 distinct geological eras and holds its respective gold-field. 



The first, and oldest known, is the hydrographical basin of the 

 Caribbean Sea, and is separated from the Orinoco basin by the 

 Coast Range of mountains. This range is the prolongation east- 

 wards of the Cordillera Occidental, and geologically, is of the 

 same age as that of the mahi Andes ; namely, miocene tertiary, 

 — that is to say, these mountains are understood to be of several 

 ages in their uplifts, the later being as late as the beginning of 

 the tertiary. Fossils indicating this position have been found at 

 Carupano, Maturin, and other points, on the main land, and on the 

 Island of Trinidad, according to R. L. Guppy. The central axes 

 of these mountains are metamorphic, and probably metamorphosed 

 paleozoic. Gold, silver, copper, lead, and other ores are found in 

 their rocks. 



In the absence of positive data, and reasoning by analogy from 

 other portions of this range, the auriferous veins are as late in 

 time as the Silurian, according to Prof. Forbes, 



The hydrographical basin of the Orinoco is filled with much 

 older rocks ; nameh% crystalline mainly ; so far as known to our 

 party, they are gneiss and gneissoid; save in the vicinity of Cia- 

 coa, where tertiary obtains, no other rock has been seen. 



A section from the Orinoco, from the village of Las Tablas, 

 southward to the summit of the Imitaca Range, reveals only 

 gneissoid rocks. 



