370 Reviews — Ca2:)t. C. E. Button — 



accidental, and it is not necessary that, in order for valleys to exist, 

 the rocks should be stratified at all. A diaclinal valley is thus 

 described as one cutting across an anticlinal fold ; but as this is 

 found to include two of the other systems of the author — namely, 

 cataclinal, in the direction of the dip — and anacUnal, running against 

 the dip of beds — the subject is hardly worth following further than 

 to say that possibly some such names as a " synclinal valley,'' i.e. one 

 running on the axis of a synclinal fold or its converse, might be 

 found useful as short descriptive terms, if dissociated from the idea 

 that their existence was due to any law connected with the folding 

 of beds, rather than to accidental circumstances. 



As far as the geology of the region can be gathered from these 

 pages, it appears that the country has a basement of granitic or 

 metamorphic rocks called granite by the author, though he tells us 

 they are not granite, but crystalline schists, with dykes and beds of 

 greenstone and granite ; these are succeeded by unconformable beds 

 of vitreous sandstone 10,000 feet in thickness, again unconformably 

 overlain by several thousands of feet of the Carboniferous, Triassic, 

 (possibly), Jurassic, Cretaceous, and Tertiary formations. 



The volume is accompanied by a sketch-map of a part of 

 the country explored, and a profile showing the relative difference 

 in the form and elevation of the ground adjoining the Colorado and 

 Mississippi rivers. It is to be welcomed as an important contribution 

 to our knowledge of a highly interesting terra incognita, and 

 perhaps as an earnest of further geological details, for which the 

 author appears to have collected materials, which, read by the light 

 of modern and moderate information, may prove a valuable addition 

 to recent research. 



II. — Critical Observations on Theories of the Earth's Physical 

 Evolution (concluded). By Capt. C. E. Dutton, U.S.A. (The 

 Penn Monthly. Philadelphia, June, 1876.) 



Second Notice. 



THE first part of these " Observations," which appeared in the 

 May number of the Fenn Monthly, was noticed in our last 

 issue. The concluding portion has since been published, and our 

 readers will no doubt be interested to learn what Captain Dutton 

 has to offer in place of the " contractional hypothesis," against 

 which he has advanced so many weighty objections — remarking 

 by the way that these objections lie not so much against every form 

 of the '' constructional hypothesis," as against those which attribute 

 the diminution of the earth's volume to mere cooling ; and especially 

 to that which assumes the cooling to have affected a solid earth, devoid 

 of any liquid substratum beneath the superficial crust. They will, 

 upon perusal of what follows, probably agree with us, that, although 

 in his former article he declines claiming for his forthcoming views 

 the dignity of a theory, they nevertheless deserve that appellation. 



Eejecting the contractional hypothesis, and assuming that the 

 cooling of the earth is still in its earlier stages, it will follow that 

 alternations of emergence and submergence, and those elevations and 



