280 Revieivs — Geology of Minnesota. 



rocks. The original matter of the paper is chiefly to be found 

 under the last head, and iu an appendix on infiltrations in Quater- 

 nary deposits. 



All the sections described seem to bear out the author's views 

 very completely, but since many competent observers have failed 

 to admit them in certain cases, such as that of the Eed Drift of 

 Paris, which Professor Hebert declines to regard as altered Grey 

 Drift, it must be concluded that the evidence is not always so clear 

 and satisfactory. But although all Mr. Vanden Bi'oeck's examples 

 may not be accepted as pi"oven by those specially conversant with 

 the detailed structure of the many districts whence they have been 

 collected, there is no reason to doubt the general truth and the 

 important nature of his thesis. Indeed, illustrations are not wanting 

 in England, as in the case of the shelly Eed Crag of Suffolk, where 

 Mr. Whitaker has shown that the supposed line of erosion between, 

 it and a certain unfossiliferous sand is really a line of dissolution 

 of shells, the sand being simply Eed Crag deprived of its fossils 

 through the percolation of water.^ 



On the whole, Mr. Vanden Broeck's Memoir must be welcomed as 

 being, up to the present, the most complete epitome of a class of 

 facts of considerable geological importance, which had been singularly 

 neglected and ignored, until our author took them in hand in his 

 own vigorous and enthusiastic manner. 



It may be added that Mr. Vanden Broeck would be glad to receive 

 information as to any new facts or objections relating to the subject 

 of his Memoir. Gr. A. L. 



III. — The Geology of Central and Western Minnesota. A Pre- 

 liminary Eeport by Warren Upham, Assist, on the Geol. and 

 Nat. Hist. Surv. of the State, under the direction of Prof. N. H, 

 Winchell, of the State University. From the General Eeport 

 of Progress for 1879. 8vo. pp. 58. 

 TTNDEE a rather unpromising exterior, this memoir includes 

 \j several matters of special interest. It will also attract atten- 

 tion from the fact that it is the first report of the first student of 

 Glacial Geology ever officially employed in his special capacity for 

 a considerable period, and in a region over most of which glacial 

 deposits prevail exclusively. 



In consequence of the paucity of natural exposures (which is a 

 circumstance not to be deplored, since natural sections are so 

 generally misleading), recourse has generally been had to artificial 

 excavations, mainly wells, in determining the character of the glacial 

 deposits. The records of no less than 582 wells have been examined 

 and digested in the preparation of the report. A compact lower 

 till, usually blue, and a less compact upper till, usually yellow or 

 brownish, both containing considerable intercalated sandy and 

 pebbly layers, are recognized as of general extent ; and local deposits 

 of modified drift, often presenting a kame-like aspect, are also 

 described. Inter-glacial beds, containing soil, wood, plants, and 

 1 See Quart. Journ. Geol. Soc. Lond. vol. xsxiii. p. 122. 



