68 Scientific Intelligence. 



latter two adjoining the gneiss but unconformable to it. Above 

 these there follow: with over-lap unconformity, (1) the "Ta- 

 conic" beds stated to be of the Olenellus horizon, and including 

 the Animike and Huronian ; (2), with over-lap unconformity, the 

 "Potsdam" including quartzytes (with gabbro and red granite), 

 referred to the Paradoxides horizon, on the ground of fossils 

 reported from the Pipe clay district of southwestern Minnesota 

 at the southwestern extremity of the belt; (3) the " St. Croix" 

 beds, " of the Dikelocephalus horizon " with only over-lap un- 

 conformity between them and the Potsdam, and graduating above 

 into the Calciferous magnesian limestones. 



Prof. Wmchell makes the beds of iron ore of the Animike to 

 correspond in age and relation to iron ore-beds in the Taconic 

 formation of western New England. But this formation has no 

 such beds, the only iron ore being limonite, of secondary origin, 

 except some local bodies of iron carbonate. Moreover the Taconic 

 limestone, in which the limonite deposits and iron carbonate 

 occur, has afforded in some places Calciferous or Trenton fossils. 

 The latest discovery of this kind was made in 1889 by W. B. 

 Dwight (this Journal, xxxviii, 150), in the Copake-Millerton- 

 Amenia limestone-belt, in which are several of the great limonite- 

 deposits, and at Amenia the largest body of iron-carbonate yet 

 observed in the Taconic region ; and here the fossils of the lime- 

 stone were species of Ophileta, Orthoceras, Cyrtoceras. 



There is a misapprehension on page 9, that should be noticed. 

 It is there stated that a second edition of Dana's Manual of 

 Geology was issued in 1864, two years after the first. The 

 author of the work knows nothing of such a second edition. 

 There was an issue of the work that year from the stereotype 

 plates, and the publishers may have inserted 1864 on the title 

 page; but if so, it was not a new edition. Moreover such a 

 method of moving on the date the author has always protested 

 against. j. d. d. 



3. Geology of the Quicksilver Deposits of the Pacific Slope. 

 486 pp. 4to, with a folio atlas of 14 plates, by George F. Becker. 

 Vol. xiii, Monograph of the U. S. Geological Survey. — In his 

 report Mr. Becker treats of two subjects of prime geological 

 importance — that of the metamorphic Cretaceous rocks of Cali- 

 fornia, and the related one, the origin of the deposits of quick- 

 silver. The former he had previously presented, but less fully 

 and less strongly; in this new volume the facts are so clearly 

 set forth, and are so well fortified, the gradations from non- 

 metamorphic to metamorphic made so plain, that all doubts 

 should disappear even from those who have been relegating all 

 serious rock-crystallization to Archaean time. The metamorphosed 

 rocks are proved by fossils to be for the. most part at least Lower 

 Cretaceous or Neocomian in age ; and in constitution they were 

 granitic sandstones and shales, containing feldspar, quartz, and 

 more or less mica, with often hornblende. The new minerals 

 made by the metamorphism include muscovite, augite, hornblende, 



