REVIEWS 683 



appeared too recently to have been included. This and certain other 

 parts of the volume dealing with geological nomenclature and the time 

 scale apply the views which Dr. Ulrich has advocated for a decade 

 regarding the shifting of the Ordovician-Silurian boundary downward. 

 Consequently the Silurian of much of this volume is not the Silurian of 

 the textbooks nor of the reports of most other state, provincial, and 

 government surveys of North America. It is the Silurian of most other 

 authors and reports plus the part of the Ordovician known as the Rich- 

 mond in the Ohio valley and the Queenston shale in New York-Ontario 

 sections and the Juniata in Pennsylvania. This revision considerably 

 more than doubles the thickness of the Silurian system in western New 

 York. 



The writer has somewhat the same interest in this alteration of the 

 geological time scale which he would have in a proposal to lengthen the 

 month of June by adding a couple of weeks from the month of July. If 

 the State of Maryland wishes to have either a geological time scale or an 

 almanac which differs radically from those generally used elsewhere that 

 is her privilege, but the writer hopes that other states will not add to the 

 confusion by following the example of some of the authors of this volume 

 in redefining the Silurian system. 



It must be added that it is not quite clear from the volume itself 

 whether this revision of the Ordovician-Silurian boundary represents the 

 official viewpoint of the Maryland Survey, or only a courtesy or privilege 

 allowed two of the authors. A map labeled " The Silurian Formations of 

 Maryland" which includes the Juniata formation and bears the State 

 Geologist's name appears to support the first-named inference; but since 

 it is incorporated in a report of Dr. Swartz, who adheres in his delimita- 

 tion of the Ordovician-Silurian boundary to the customary usage, the 

 reader closes the volume with a rather hazy idea as to just what the 

 Maryland Survey's official attitude is on this question. The policy of 

 leaving each author entire freedom in matters of nomenclature, which 

 appears to have governed in the preparation of this volume, looks well 

 from the standpoint of individual liberty but its weakness lies in the fact 

 that it leads toward general chaos. The bewildering effect of two schemes 

 of geological nomenclature in the same volume well illustrates the great 

 need of geologists' getting together and using a nomenclature which is 

 generally recognized. 



Intimately connected with the revision of the Ordovician-Silurian 

 boundary as defined by two of the authors of this volume, is the use of 



