86 Revieics — Professor 8/iaIer's Outlines of Earth History. 



countries are introduced their true meaning is altered and confusion 

 arises. Such has been the case with terms like Cenomanian, 

 Portlandian, Kimeridgian, and Callovian. The term Portlandian 

 should only be used for the period represented by the Portland 

 Beds of Portland, the Callovian for the period represented by the 

 Kellaways Beds of Kellaways, and so on. 



The student who peruses Mr. Marr's handy book will be prepared to 

 encounter numerous difficulties, but his path will have been smoothed 

 by the many useful explanations and suggestions, and he will be 

 prepared to weigh the possibilities and probabilities before coming 

 to definite conclusions. After all, the chief difiiculties which beset 

 the student are not in the folds and overthrust faults which locally 

 interfere with the true sequence, nor in the determination of the 

 method of origin of the strata, nor even in the correlation of 

 formations when the organic remains have been carefully studied 

 and determined. The greatest difiiculties ai'e in the identification of 

 species amid the "tangled mazes of the synonymy"; and the best 

 chance of doing good work in stratigraphical geology is to specialize 

 on formations and faunas, aiding local research by a study of what 

 lias been done in other parts of the world. To endeavour to do 

 a little well must be the aim of all students, and Mr. Marr's work 

 will surely aid the enthusiastic inquirer in dealing with the many 

 problems which come before him. 



III. — Outlines of the Earth's History : A Popular Study in 

 Physiography. By N. S. Shaler, Professor of Geology in 

 Harvard University. 8vo ; pp. iv, 417, with 10 full-page 

 Illustrations and 23 Figures in the text. (London : W. Heine- 

 mann, 1898.) 



rpHE object of this book, as stated in the preface, "is to provide 

 JL the beginner in the study of the earth's history with a general 

 account of those actions which can be readily understood, and which 

 will afford him clear understandings as to the nature of the processes 

 which have made this and other celestial spheres." The treatment 

 of this widely embracing, one might almost say boundless, subject 

 is bi'ought within the compass of nine chapters, the titles of which 

 will give a clue to their contents. The first is an introduction to 

 the study of Nature, followed by a somewhat abstrusely historical, 

 rather than practical, account of the ways and means of studying it. 

 The succeeding chapters are on the Stellar Realm ; the Earth ; the 

 Atmosphere; Glaciers; the Work of Underground Water; the Soil; 

 and lastly, the Rocks and their Order. Under these heads very good 

 descriptions are given of the most important natural phenomena, 

 and they are principally illustrated by examples to be found in 

 North America, which, though less likely to be familiar to students 

 in this country, are oftentimes of a more striking and representative 

 character than instances drawn from more limited arefis. To 

 some of the statements given exceptions might be made ; for 

 example, that the floors of the deeper seas are plentifully scattered 



