Reviews— A. W. Rogers — Geology of Cain Colony. 137 



The classification of A. G. Bain is adhered to. The figures of fossils 

 from the Bokkeveld beds are a welcome addition. 



The Karroo formation, forming unquestionably one of the best 

 known rock groups in South Africa, receives full attention. It is 

 somewhat startling to read that at present there is no very satis- 

 factory classification of these rocks. The chapter by Professor 

 Groom on the reptiles of the Karroo formation will therefore be of 

 much value, for, as is well known, these animals mark distinct 

 horizons. As is fitting, considerable attention is paid to the intrusive 

 dolerites and allied rocks of the Karroo system, for besides being 

 a distinctive feature of the Karroo country they present problems 

 the petrologist has not solved. The author does not support the 

 absorption theory for the intrusive masses of Pondoland and East 

 Griqualand. Plate xvi, showing columnar structure in Dwyka 

 conglomerate produced by an overlying sheet of dolerite, might 

 readily be used to controvert the knowing. 



The knowledge of the rocks of the Cretaceous system is brought 

 up to date in chapter viii. Good illustrations of the typical fossils 

 are given, while Dr. F. L. Kitchin supplies notes on the relation- 

 ship of the marine fossils to those of foreign Cretaceous faunas. 

 The chapter on the volcanic pipes younger than the Stormberg 

 Series (summit of the Karroo) includes a short account of the 

 diamond pipes of the Kimberley area. The author considers that 

 these great explosions occurred "at some period after the close of 

 Stormberg times (probably after the Uitenhage period)." 



A chapter on the Eecent deposits, including that of the vleys and 

 pans, concludes the detailed description of the geology. It is 

 followed by a summary of the geological history of the colony. 

 Subjects of a more speculative character are here dealt with, among 

 which we note that the period of great mountain-building in South 

 Africa succeeded the Ecca beds (Permo-Carboniferous) and occurred 

 somewhere between this and the Uitenhage (Lower Cretaceous) period, 

 possibly between the Ecca and Beaufort (Permo-Triassic) periods.^ 



Each of the chapters forms a treatise in itself, and the reader 

 interested in any particular formation will readily find what be 

 seeks, while for fuller detail he is referred to the standard works 

 given in the appendix. 



The volume is illustrated throughout by numerous plates of 

 admirably reproduced photographs of rock scenery and rock structure. 

 The figures of fossils are clearly drawn. The horizontal sections 

 are somewhat meagre and not impressive, owing to the necessarily 

 small scale adopted for the vast distances represented. On the coloured 

 geological map, which is clearly printed, the number of place-names 

 is far too small. A few topographical maps would materially assist 

 the reader. The notes on the geology of some of the railway lines 

 given in chapter xii seem out of character with the rest of the work, 

 and would be better as an appendix. The book needs a more copious 

 index. 



^ Age given in the brackets is ours. 



