170 SCIENCE PROGRESS 



that the average composition of sediments demands a dual parentage composed of 

 65 per cent, of granite and 35 per cent, of basalt. Such rock on decomposition 

 and sorting yields 82 per cent, of shale, 12 per cent, of sandstone, and 6 per cent, 

 of limestone. To express the redistribution more accurately — 



100 grams igneous rock 



5'3 » C0 2 



20 „ H 2 



I'o „ 2 



°7 „ C 



o'3 „ S0 3 



o - i „ other substances^ 



yield 



87-8 grams Shale 

 I2'9 „ Sandstone 



67 „ Limestone 



2"o „ Oceanic salts, etc. 



109/4 grams 



Metamorphism as understood in Europe is divided into dynamic and thermal 

 anamorphism, though it is admitted that usually the distinction is difficult to define. 

 A chapter is devoted to textural and structural changes, and the views of Becke 

 and Grubenmann are discussed and criticised at some length. The authors show 

 that anamorphic changes in sediments are in the general direction of a return to 

 igneous rock composition, but they recognise that the assemblage of minerals in 

 schists and gneisses differs both quantitatively and qualitatively from those of 

 igneous rocks. Unless actual fusion takes place, as in stoping or marginal 

 assimilation, the metamorphic cycle is not known to be closed. 



The various criteria employed in determining the origin of schists and gneisses 

 are thoroughly examined, and it is shown that no one criterion can usually give a 

 conclusive result. A welcome feature in the presentation of the subject-matter of 

 the book is the treatment (already strongly advocated in this country by Mr. 

 T. Crook) of ore deposits as rocks. 



The authors are to be congratulated on the production of a lucid and logical 

 account of metamorphism, for with all the limitations of their methods they have 

 covered the whole subject in such a way that the reader cannot fail to grasp the 

 essentials of every change and to realise its place in the pulsating evolution 

 of rocks. 



Arthur Holmes. 



Biology. By Prof. Gary N. Calkins, Ph.D. [Pp. viii 4- 241, with 101 figures.] 

 (New York : Henry Holt & Co., 1914. Price ys. 6d. net.) 



Prof. Calkins in Biology provides the student with an introduction to 

 biological studies, and the method he adopts is to treat a number of types of the 

 lower animals and plants. The type system has great advantages for instructional 

 purposes, more especially when accompanied by well-arranged laboratory 

 exercises, but in many cases it tends to produce a course that is no longer justly 

 described as biology but becomes rather comparative morphology and anatomy. 

 This volume is far from doing that, for the problems are all approached from the 

 physiological point of view, and as the author claims " animal differentiation for 

 the performance of primary functions of protoplasm is the main theme of the 

 entire course." It therefore forms an excellent complementary work to be read 

 in conjunction with the ordinary biological text-books generally in use in this 

 country. 



The main types dealt with are, Yeast, Bacteria, Amoeba, Chilomonas, 

 Paramecium, Hydra, Lumbricus, Homarus, Taenia, Pleurococcus, Sphcerella 

 and Pteris, but other forms are briefly referred to in dealing with certain points. 

 Each type is dealt with morphologically and histologically first and then physio- 

 logically, and finally most of them are utilised to illustrate some biological 



