Geology. 413 



fornia to Alaska, dwelling at length on the Muir glacier which 

 was the one the author investigated. It next treats of the Green- 

 land ice, in whose features the condition of the Ice-age are most 

 nearly exhibited, and then of glaciers in Europe and other lands. 

 After this introduction, extending over more than a hundred 

 pages, the evidences and events of the Ice-age in North America 

 are discussed at length with some account also of the facts from 

 Europe. The position of the southern limit of the ice is described 

 in detail and partly from personal observations, especially in 

 Pennsylvania, Ohio, Indiana and Dakota. Afterward, the effects 

 produced by glacial erosion and transportation are reviewed, the 

 former including, in the author's opinion, many lake basins as 

 well as river channels, and the latter comprising accumulations of 

 debris into drumlins and kames. Other chapters treat of the 

 buried valleys and extensive changes in river courses as a result 

 of glacial depositions, — changes that led to the production of 

 many of the waterfalls of the country, even the largest; the geo- 

 graphical march of vegetable and animal life consequent on the 

 advance and retreat of the glacier; the cause of the glacial cli- 

 mate, under which subject Croll's theory is considered and no 

 theory is found to be satisfactory ; the date of the Ice-age ; the 

 antiquity of man. It is shown pretty satisfactorily that accord- 

 ing to evidence from the rate of erosion at Niagara Falls, the St. 

 Croix Falls, and from other facts, that the Ice-age probably closed 

 from 8,000 to 10,000 years back, and it is inferred, from less 

 clear proof, that only 15,000 to 25,000 years have elapsed since it 

 began. The chapter on human i*elics in America reaches the 

 conclusion that the earliest of them occur in deposits of the 

 Glacial era, some thousands of years before its close. 



An Appendix contains the views of Mr. Uphain on "the prob- 

 able causes of glaciation." 



With regard to the Glacial period there is on several points 

 wide diversity of opinion among geologists, and much is yet to 

 be learned, and some of the conclusions of the author will find 

 opponents. But the work, nevertheless, is a valuable review of 

 the marvelous events of the Ice-age. 



3. Annual Report of the Geological Survey of Arkansas for 

 1888, John C. Brenner, State Geologist. Vol. II. The Neozoic 

 Geology of Southwestern Arkansas, by Robert T. Hill, Assistant 

 Geologist. — The whole breadth of southern Arkansas and more 

 than half of middle and northern are underlaid by Cretaceous 

 and later deposits — a part of those of the great Mississippi bay 

 of the Cretaceous and Eocene-Tertiary periods. The Report of 

 Professor Hill treats of the distribution and stratigraphical fea- 

 tures of the Cretaceous, Tertiary and Quaternary deposits in the 

 southwestern portion of the State, the term Neozoic as used by 

 him including the uppermost Jurassic, Cretaceous, Tertiary and 

 Quaternary strata of the region. The Cretaceous formation has 

 two divisions, as already explained by Mr. Hill* in this Journal, 



* Vol. xxxiv, 287, 1887; xxxvii, 282, 1889. 



