REVIEWS 339 



It may be valued locally for its sections of pits which are notoriously liable to 

 change or destruction. The author supports the view that the boulder clay and 

 the contorted beds of the Cromer coast are products of floating ice. His main 

 thesis, however, is that, " whatever their origin, the beds of the Norfolk cliffs can 

 be traced up to the East Anglian peneplain, and that the Boulder Clay and 

 Plateau Gravel are only part of one and the same series." Owing to the irregular 

 and intermittent nature of earth bulges and depressions, he does not hope to trace 

 any type of deposit in East Anglia as contemporaneously formed over a wide area, 

 though the succession of types in different areas may be the same. We gather 

 that the indications of climatic change in our Pleistocene beds, including those 

 of the Glacial epoch, are ascribed to comparatively small oscillations in the level 

 of the land and in the relations of land and water. 



Methods in Practical Petrology. By H. B. Milner, B.A., F.G.S., F.R.G.S., 

 and G. M. Part, B.A., F.G.S., F.R.G.S. [Pp. 68, with 6 illustrations.] 

 (Cambridge : W. Heffer & Sons, Ltd., 1916. Price 2s. 6d. net.) 



This little book purports to be a practical companion to standard works on 

 petrology. Its practical methods, however, resolve themselves into a somewhat 

 trite series of directions for the preparation and examination of thin sections of 

 rocks, the use of micro-chemical methods (staining), and the mounting of sands 

 and crushed rock material. These hints will no doubt be useful to the student 

 in elementary petrology ; but in a book of barely 20,000 words it would have been 

 wise to have severely limited the matter to practical methods, and not have tried 

 to cram in ineffective notes on rock composition and classification, with tables of 

 refractive indices and birefringences of minerals. There is an appendix on 

 methods of preparing stains which is unnecessary, for even now it is easier for 

 the student to procure stains than to make them himself. Moreover, micro- 

 chemical methods are rarely used in comparison with the more exact optical, and 

 are useless save in expert hands. The authors state that very little literature on 

 these practical methods is available to the student, but they have omitted to give 

 a reference to the best, biggest, and latest work on this subject — Johannsen's 

 Petrological Methods. There are misprints on pp. 8, 13, and 39, and " siliceous" 

 is misspelt throughout on the latter page. The book is most likely to be useful in 

 the sections devoted to the mechanical preparation of material for petrological 

 examination. 



G. W. T. 



ZOOLOGY 



The Rat. Reference Tables and Data for the Albino Rat (Mus norvegicus albinus) 



and the Norway Rat {Mus norvegicus). By Henry H. Donaldson. 



[Pp. v + 278.] (Memoirs of the Wistar Institute of Anatomy and Biology, 



Philadelphia, 19 15. Price 83.) 



THOSE who use either the albino rat or the brown rat for the purposes of 



experimentation will find a mine of useful information in this volume by Mr. 



Donaldson. The author, whose own works on the subject and those of his 



collaborators are now widely known, has brought together all the information 



concerning these two varieties of Mus norvegicus that has been or is capable of 



being treated statistically. It is essentially a book of reference and as such is 



arranged in a very convenient way and has a full index. The bibliography of 



52 pages is not only extremely valuable in itself, but gives an indication of the 



