746 JOURNAL OF GEOLOGY. 



most geologists. He thinks that the strongest evidence for the exist- 

 ence of life in pre-Cambrian time is the high organization of the 

 Cambrian fauna. While geologists will be ready to assent to the 

 -strength of this last argument, they will hardly be ready to regard 

 it as the only strong reason for belief in pre-Cambrian life. To the 

 very considerable number of fossil forms already found in pre-Cam- 

 brian rocks no reference is made. 



The important question of the origin of the Archean is rather 

 briefly dismissed. The discussion touching this question is much less 

 full and much less satisfactory than that of Prof. Van Hise, recently 

 published. 1 Indeed, had Prof. Van Hise's discussion been pub- 

 lished before Dr. Kayser's treatise, the latter author might have found 

 a way out of some of the difficulties which seem to lie in his mind con- 

 cerning the origin of the Archean. 



An excellent feature of the book is the prefacing of the discussion 

 of each system by a short account of the origin and history of its 

 differentiation from underlying and overlying systems. Each system 

 is discussed under the general heads of — i) Distribution and devel- 

 opment ; 2) Paleontology. Under the first head, it could have been 

 wished that the structural relations of the systems had been more 

 uniformly and sharply brought out. Such clear statements as that 

 concerning the North American Devonian system, that it rests "con- 

 formably and without break on the Silurian, and is covered conforma- 

 bly by the Carboniferous " (page in), are not always to be found. 

 Where knowledge does not permit such positive statements, definite 

 statements representing the degree of present knowledge would have 

 been welcome. So, too, the relations of faunal and stratigraphical 

 breaks are not always so clearly set forth as could have been desired 

 in a text-book. 



In the discussion of the Permian system, Dr. Kayser brings out 

 the fact of wide-spread conglomerate formations (India, Victoria, Bra- 

 zil, South Africa) in tropical latitudes and the southern hemisphere, 

 which sometimes contain polished and striated stones very like those 

 of glacial formations of later date. In Africa the Dwyka conglomer- 

 ate rests on rock, the upper surface of which is smoothed and striated 

 like rock beneath the modern glacial drift. Dr. Kayser indicates that 

 the belief that these Permian conglomerate beds are of glacial origin 

 has gradually gained ground. The flora succeeding the conglomer- 



1 Bulletin of the U. S. Geol. Survey, No. 86. 



