566 Reviews — Dr. G. F. Wright — Ice Age in North America. 



rocks that show this property and yet cannot possihly be termed 

 laterite, although they probably contain a certain quantity of 

 hydroxides of iron and aluminium, to the dehydration of which the 

 setting of laterite is usually ascribed. 



9. .For any rocks (such as some of the pisolitic limonites), associated 

 with the laterite formation, that have probably been formed by 

 chemical deposition in lakes or bogs the name lake laterite is suggested. 

 This is regarded as an unimportant variety of laterite. 



10. Certain lateritic rocks that have been formed by the nieta- 

 somatic replacement at the outcrops of a variety of rocks, and which 

 cannot be regarded as residual products of the decomposition of the 

 underlying rocks, have been designated lateritoid. Such rocks can 

 usually be recognized by their preserving unaltered or but partly 

 altered fragments of the underlying rocks, and of retaining signs of 

 the original bedding-planes of the rocks they have replaced. They 

 have hitherto always been found on the upturned outcrops of the 

 quartzites and argillaceous schists and phyllites of the Dharwar 

 formation, and usually take the form of iron-ore or manganese-ore, 

 alumina not being an abundant constituent of the lateritoids. 



11. Rocks formed by the accumulation of detritus from masses of 

 chemically-formed laterite (or of lateritoid) either alone, or mixed 

 with extraneous materials, such as fragments of quartz or gneiss, may 

 be termed detrital laterites, as an alternative to which the term 

 lateritite is suggested. 



12. Most of the so-called laterites of the Guianas as described by 

 Harrison and Du Bois are not true laterites unqualified, but are either 

 quartzose or lithomargic laterites, or lateritic earths. Many of them 

 are detrital rocks, sometimes rich enough in lateritic material to be 

 called detrital laterite or lateritite. True laterites do, however, also 

 occur. 



13. The classification of laterites and associated rocks put forward 

 in this paper is, of course, of a more or less tentative natui'e, and 

 although it is believed to be a workable system of nomenclature, yet 

 future work will doubtless show the desirability of various modi- 

 fications and amplifications. 



EEVIEWS. 



I. — The Ice Age in North America and its Bearings upon the 

 Antiquity of Man. By G. Frederick Wright, D.D., LL.D. 

 Fifth Edition. 8vo; pp. xxi, 763, with 10 plates, 3 maps, and 

 196 text-illustrations. Oberlin (Ohio), Bibliotheca Sacra Company; 

 London, Charles Higham and Son ; 1911. Price 20s. net. 



ANEW edition of Dr. "Wright's great work will be widely 

 appreciated by students and teachers, giving as it does such 

 a clear and comprehensive view of the grander features in Glacial 

 geology that are so well exhibited in North America. Although, as 

 the author remarks, later investigations have not seriously affected the 

 main theories adopted in 1889, when the first edition of his work was 

 published, yet there have been further destructive criticisms of 



