REVIEWS 173 



be mentioned that, since the publication of the book, it is rumoured that an 

 entirely different opinion as to the age of these implements has been formed by 

 another competent observer who has studied them on the spot. 



The book is further enlarged by an appendix in which the author defines 

 at length the terms " Eolithic," " Palaeolithic," and " Neolithic," as representing a 

 sequence of periods in Europe. 



On the whole, the second edition of Mr. Johnson's book — now grown to eighty- 

 five pages — will be welcomed by those who are interested in the comparatively 

 new study of the archaeology of savage Africa ; and, while it cannot be said 

 that the sequence he claims is yet absolutely clear, the fresh data which he has 

 obtained are in themselves ample excuse for a second edition. A general map 

 showing localities of finds, and an index, would be valuable additions to any 



future issue. 



T. Athol Joyce. 



Text-Book of Petrology, containing a Summary of the Modern Theories of Pedo- 

 genesis, a Description of the Rock-forming Minerals, and a Synopsis of the 

 Chief Types of the Igneous Rocks and their Distribution, as illustrated by 

 the British Isles. 5th Edition. By F. H. Hatch, Ph.D. [Pp. xvi + 404.] 

 (London : Sonnenschein, 1909. Price ys. 6d. net.) 



Dr. Hatch has produced a useful introduction to the study of the igneous rocks. 

 In the first part he describes their structure, texture and genesis, and endeavours 

 to place the student au courant with the recent work that is beginning to throw 

 some light on the process of their crystallisation. The second part is devoted to 

 the rock-forming minerals, and is of somewhat more elementary character than 

 the rest of the book. Nowhere are the symbols of the faces supplied, although 

 every student is now presumed to be acquainted with the Miller notation. It is 

 gratifying to see that the author retains the familiar form kyanite, instead of 

 following Dana in adopting the spelling cyanite. The latter, due to Werner, has, 

 it is true, priority, but it is apt to be given a pronunciation which is indistinguish- 

 able from that of syenite. There is really no satisfactory ground for representing 

 the Greek k by c in English, except in old-established words which have come to 

 us by way of Latin or French. It not only tends to obscure the derivation and 

 assimilate the sound of words of different origin, but more often than not it intro- 

 duces an unnecessary divergence between the nomenclature in use in this country 

 and that employed by the majority of Continental workers. 



In Part III. we enter on the substantive portion of the book, the classification 

 and description of the igneous rocks. It is to be regretted that the author retains 

 the customary primary division into plutonic, Iiypabyssal, and volcanic rocks instead 

 of following the examples of Prof. Bonney and Prof. Weinschenk in grouping 

 together rocks of similar chemical composition which have consolidated under 

 different conditions. He carries out his classification so rigidly that he will not 

 even allow the peridotites a place among the plutonic rocks, on the ground that 

 they only occur in dykes ; a contention that can hardly be maintained in view of 

 the massive development of dunite and serpentine in some localities. 



He next separates each of his main divisions into a number of families according 

 to their mineral composition. It would have rendered the classification easier 

 to grasp and remember if the limits of the families had been the same in each 

 division. As it is, there are six families of plutonic rocks, fourteen of hypabyssal 

 and seven of volcanic rocks. The families are divided into subfamilies, and these 

 again into types, which are briefly but clearly described, though subdivision is 



