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The most important change made in the classification, as formerly 

 used, is the breaking up of the old Cuyahoga formation into the Orange- 

 ville formation, Sharpsville sandstone, and Royalton formation, while 

 the Sunbury shale becomes merely a subdivision of the Orangeville. 

 The two lower divisions of the Cuyahoga are considered to be the western 

 extensions of the formations of the same names in western Pennsylvania, 

 while the Royalton formation is apparently the Meadville, with perhaps 

 also the Shenango, of the Pennsylvania classification. 



This volume is by far the most important stratigraphic publication 

 issued by the Geological Survey of Ohio in recent years. It deals with a 

 part of the state which has been very much misunderstood by many of 

 the former workers in that region and therefore misrepresented to the 

 geological world. Undoubtedly the greatest importance of the bulletin 

 lies in its bearing on the boundary line between the Devonian and 

 Mississippian of Ohio, which is still a subject of much controversy. It 

 appears that Dr. Prosser favors drawing this line at the base of the Berea 

 sandstone, but he makes the statement that he "has not yet reached a 

 positive conclusion concerning the age of this [Bedford] fauna," which is 

 now used as marking the introduction of Mississippian sedimentation. 

 The reader is therefore allowed to draw his own conclusions from the 

 evidence presented. 



C. R. S. 



Geologische Dijfusionen. Von Raphael Liesegang. Dresden und 

 Leipzig: Theodor Steinkopf. 



The newer advances in mineralogy and petrology owe much to the 

 work of the German chemists during the last quarter of a century. One 

 of the most recent fields of investigation, which German workers have 

 made peculiarly their own, is colloidal chemistry. The field is yet so 

 new that geologists are only now beginning to realize the importance of 

 its applications to their own science. At such a stage a book written 

 from the point of view of the colloidal chemist is decidedly welcome. 

 While it is today impossible for one man to be a specialist in two sciences, 

 it is in the best interests of scientific progress that the applications of 

 this branch of chemistry to geology be first made by an authority on col- 

 loids, rather than by a geologist. A study of the book before us is cal- 

 culated to convince those who may be skeptical on this point. 



The very special value of the book to the geologist lies in the detailed 

 description of such experiments on the diffusion of colloids as may have 



