526 THE JOURNAL OF GEOLOGY. 



nomena of each of the regions with which he is familiar, together 

 with the reasons therefor. The failure to summarize and interpret the 

 summaries of the literature reviewed has lessened the value of some of 

 the essays of this series. 



The plan of the volume is simple. It consists of, first, a digest of 

 all the papers on the pre -Cambrian geology of North America which 

 had appeared at the time the manuscript left the author's hands ; sec- 

 ond, a discussion of the literature ; and, third, a discussion of the gen- 

 eral principles involved in the study of pre -Cambrian rocks, together 

 with a statement of the results which have already been attained in 

 America in the application of these principles. 



The digests of the literatures are grouped on a geographical basis. 

 The digest of all publications bearing on the pre -Cambrian geology of 

 the original Laurentian and Huronian areas constitute one chapter, 

 and the digests of the literature of the Lake Superior region, of the 

 great northern area of Eastern Canada and Newfoundland, of the isolated 

 areas in the Mississippi Valley, of the Cordilleras, and of the Eastern 

 United States, constitute each a separate chapter. Within each area 

 the digests are arranged chronologically. At the close of each chapter, 

 or in some cases at the close of their subdivisions, are summaries of the 

 results thus far attained in the respective areas. In all cases the digests 

 appear to be as nearly absolutely impartial as it is possible for human 

 work to be. The total number of papers summarized is between 700 

 and 800. Many of them are papers of considerable length, some of 

 them being elaborate reports. When it is remembered that these 

 papers are not roughly abstracted, but that carefully considered digests 

 are presented, the amount of labor involved in the preparation of the 

 bulletin will be apparent. 



It is the final chapter which, together with the maps, will attract 

 most attention. This chapter gives a concise outline history of the 

 development of pre -Cambrian geology in America, and a clear 

 exposition of its present status. Professor Van Hise concludes that it 

 may be accepted as demonstrated that in North America there is an 

 intricate system of granites and gneisses and crystalline schists, which 

 represent the oldest rocks of the continent, and that this system under- 

 lies all known sedimentary rocks and their derivatives, and that if it ever 

 contained sedimentary materials of any sort, all evidence of their 

 existence has been obliterated. 



It is to this system of rocks that the name Archean is restricted. 



