430 SciQutiJie Intelligence. 



otlier way. This criterion would bring us right with regard to our own 

 epoch, while by avoiding it, we might be able to prove that we in Amer- 

 ica are of the Tertiary age of the world. Now, as Mr. Redfield has 

 shown, the fossil fishes, — the most characteristic species of any formation, 

 are but half heterocercal and come nearer to the Jurassic type than 

 the Triassic. There is hence reason for the opinion notwithstanding the 

 important evidence brought forward by Dr. Emmons, that the Lias period 

 may be represented by the formation ; and w^e may be nearest the truth 

 if we regard the whole formation as corresponding to the Lias and the 

 latter half of the Trias. The examinations by Mr. Heer accord with 

 this conclusion. The European subdivisions of the Trias we should not 

 look for on this continent, even if we had the whoje of the formation, 

 any more than the European subdivisions of tlie Devonian in the Amer- 

 ican Devonian. American geology is deeply interested in the decision 

 of this question, and owes much to Prof. Emmons for all that he has 

 done towards its elucidation. 



2. Illusirafions of Surface Geology ; by Edward Hitchcock, LL.D., 

 Professor of Geology and Natural Theology in Amherst College. 160 

 pp., 4to, with 12 plates of sections, maps and views. From the ninth 

 volume of the Smithsonian Contributions to Knowledge. — The subjects 

 here treated under the title of Surface Geology, are, terraces, elevated 

 beaches, drift and the associated phenomena, erosion of the surfece form- 

 ing valleys, and the agents of change, running water, the sea, icebergs 

 and glaciers. The author presents the results of a large amount of per- 

 sonal examination made mainly in New England, though to some extent 

 also in other countries. The heights and positions of numeous terraces 

 along the Connecticut valley and some of its tributaries^ and of some on 

 the Merrimack river, are given in the text, and the plates contain illustra- 

 tions both by sections and neat maps. The great subject of terraces, a 

 phenomenon that characterizes the whole breadth of the continent (ex- 

 cept perhaps at the south,) and therefore one of the grandest in the 

 science, is approached in the right method, and an important step is 

 ta"ken tow^ards solving the great problem. It is impossible in a brief no- 

 tice to give a satisfactory I'eview of the facts brought out in this long and 

 valuable paper. We mention a few of the deductions, 



1. True unstratified drift never covers the terraces ; it is covered by the 

 terrace material, and is therefore of older date. 



2. The successive "beaches'* and "terraces" are made out of the drift 

 material, with few exceptions, all by essentially similar operations. 



3. The river valleys were excavated before the terrace epoch, for in the 

 rocky gorges, as at Bellows Falls, drift scratches are found near the pres- 

 ent water level ; these gorges therefore were not closed at that time by 

 rocky barriers. 



4. The highest distinct river-terraces noticed by the author in this 

 country are as follows: at Bellows Falls, on the Connecticut, 226 feet 

 above the river ; on theDeerfield, 236 feet; on Genesee river (New York 

 State) at Mount ilorris, 348 feet. Above these heights, there are other 

 levels designated beaches, and the most distinct of these are stated to be 

 from 800 to 1200 feet high; while others, less distinct, are mentioned as 

 found at 1200 to 2600 feet in the White Mountains and elsewhere. 



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