Reviews. 



Correlation Essays, Archean and Algonkian. Bulletin of the U. S. 

 Geological Survey, No. 86. Pp. 549, 12 plates. By Charles 

 Richard Van Hise. 



In order of publication, this is the seventh of the correlation essays 

 originally planned by the survey for the International Geological Con- 

 gress of 1 89 1. If the long delay in the appearance of the present 

 essay is in any measure responsible for its excellence, no one will regret 

 that it did not appear on time. This is not the first piece of good work 

 which Professor Van Hise has done ; but he has done nothing which 

 has been of greater utility to the geological world than the present vol- 

 ume will prove to be. 



In no department of geology has there been more rapid progress 

 during the last decade than in the department in which Professor Van 

 Hise is a specialist. In no department is it more difficult for those 

 who are not specialists to follow current progress. But so successfully 

 has Professor Van Hise written his essay that the reader will have little 

 difficulty in knowing the present status of pre- Cambrian geology in 

 America. He may know definitely what is definitely known, and he 

 may know definitely what is not known. More than this, he may 

 know definitely the limitations and imperfections of facts and princi- 

 ples which are but partially worked out, without finding himself con- 

 fused between fact and possible fact, or between established principles 

 and unverified hypotheses. Consciously or unconsciously, the author has 

 given definite shape to the uncertainties and indefinitenesses of his sub- 

 ject, and in so doing has rendered an invaluable service to students. 



A mere summary of what has been done in the various areas of 

 pre - Cambrian rocks would be valuable. But the present essay does 

 much more. The author is personally familiar with much of the ground 

 brought under review in the volume, and he has given, always without 

 a suggestion of dogmatism, what every reader is glad to have, his 

 own opinion concerning the interpretations to be placed on the phe- 



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