AMERICA. 127 



" silicified forest " near Pike's Peak in Colorado. After pointing out 

 that the specimen can be shown by sections to be Coniferous, and pro- 

 bably referable to Stqiioia, the authors describe its general form, in 

 which it closely resembles a chip formed by human agency. A che- 

 mical analysis is appended, j H. A. N. 



Niles, W. H. The Physical Features of the State of Massachusetts 

 (with discussion by Dr. T. S. Hunt). Froc. Boston Nat. Hist. Soc. 

 vol. xvii. pp. 507-510. 



Orton, Prof. James. On the Geological Structure of the Amazons 

 Valley. Ann. Nat. Hist. ser. 4, vol. xvi. pp. 359-368, with 

 woodcut. [Being Chapter xli. of the forthcoming new edition of 

 his work on the Andes and the Amazons.] 

 TheValley of the Amazons is a shallow, oval basin, gently inclined from 

 W. to E., a large part of which is Hooded yearly. This basin is enclosed 

 by the slopes of the Andes and the metamorphic regions of Casiquiare 

 and Central Brazil. Probably the Coast Cordillera was the first part 

 of the Andes to be elevated, the E. range not reaching its present 

 elevation until after the Cretaceous Epoch. The characteristic rocks 

 of the maritime range are trachytes and porphyries ; those of the E. 

 range, sandstones and slate. Eaised Beaches exist upon the coast ; but 

 there are evidences of subsidence in recent times. Passing from Pacas- 

 mayo, Jurassic (?) limestone with trachytic porphyry and granite dykes is 

 met with upon the W. flanks of the coast range. Upon the E. slopes 

 Cretaceous beds are found. Eurther E. Liassic limestones occur ; and 

 the Cretaceous rocks are again found in the range of the Andes, at the 

 head of the Amazons Valley. In crossing the Andes, in the latitude of 

 Lake Titicaca, the following formations are found : — W. of the Coast Cor- 

 dilleras Oolite beds largely covered with intrusive rocks ; E. of this 

 range conglomerate, sandstone, slate, and Jurassic limestone ; then 

 Triassic and Carboniferous rocks ; and, lastly, the mass of the high 

 Andes is formed of Devonian and Silurian rocks. The valley of the 

 Amazons is uniform in character. The fundamental rock is metamor- 

 phic. Tertiary beds cover the watershed between the Amazons and 

 Paraguay ; Silurian rocks are rarely visible ; Devonian rocks occur N. 

 of the Serra of Erere ; Carboniferous fossils are found in places ; Meso- 

 zoic beds are said not to occur E. of the Andes. The valley has received 

 a deposit of clays, sands, and sandstones (Amazonian Tertiary); the 

 sandstone is now confined to the Lower Amazons. A number of fresh- 

 water and estuarine shells have been collected from this formation, all 

 the species and 12 of the genera being extinct. The author believes 

 that these beds have been deposited in a vast inland lake. E. T. N. 



Petermann, Dr. A. Die topographische und gcologische Karte von 

 Chile. [The Topographical and Geological Maps of Chile.] Fettr- 

 manns Mittheiluncjen., Bd. xxi. pp. 41, 42 ; map in two plates 

 (3, 4). 



Short account of Chilian chartography. The map (scale 1 : 1,500,000) 



