Reviews — Hatch & RastaWs Petrology. 271 



Particulars are given of the methods of mining and treatment of 

 ores, of the mineral veins and the conditions of the mineralized areas, 

 the sinter deposits, and the underground waters, and there are detailed 

 descriptions of the different mining areas and claims. 



The greater portion of the area of volcanic rocks is hilly and 

 mountainous, the highest elevation being that of Mount Kaitarakihi, 

 2,740 feet, and at one time the ground was covered by primeval forests, 

 which have been much reduced by fires. The lower grounds are partly 

 volcanic, as in the case of the Waihi plain, but are formed mostly by 

 the fluviatile and estuarine deposits, the flood-plains constituting the 

 chief arable lands. The coast is formed of precipitous cliffs with bays 

 bordered by blown sands. 



The volume is well illustrated by 10 plates of photographic views, 

 10 text-figures, and 18 geological and topographic maps, plans, and 

 sections. 



YII. — Textbook of Petbology. Yol. II. The Petrology of the 

 Sedimentary Hocks. By F. H. Hatch and li. H. Rastall. 

 With an appendix on the systematic examination of loose detrital 

 sediments, by T. Crook, pp. xiv + 425, with 60 figures in the 

 text. London: George Allen & Co., 1913. Price 7s. 6d. net. 



rpmS work is stated to be the second volume of a textbook on 

 J_ petrology, but the first has not yet appeared, unless it be 

 Dr. Hatch's earlier book on petrology issued some few years ago by 

 another publisher, and no mention is made of it in the preface. The 

 present volume is concerned with the processes and changes through 

 which sedimentary rocks have passed before they attained to the 

 position and form in whicii they are found to-day. The subject falls 

 naturally into two parts, the one dealing with the nature of the 

 deposition and the other with the after metamorphic changes. That 

 is the course followed by the authors in the present book, the second 

 part being about half as long again as the first. 



In the first chapter of the first part the authors discuss deposition 

 in general, and proceed in the remaining three to enter more in detail 

 into the three groups of fragmental, chemical, and organic deposits, 

 into which sedimentary rocks may be grouped. Many of the deposits 

 are of extreme interest and importance. For instance, the salt 

 deposits are extensively worked, and those at Stassfurt in particular 

 formed the subject of the classical researches by Van't Hoff and his 

 pupils. Again, the nitrate deposits in Chili become increasingly 

 necessary for agriculture, and their origin still remains a mystery, no 

 completely satisfactory theory having yet been put forward. The 

 coal deposits are, of course, of primary importance as the principal 

 source of heat and power; the vexed question of their origin is 

 touched upon. 



The second part is devoted to the metamoi'phic changes that have 

 taken place in the rocks after they were deposited, and successive 

 chapters deal with metamorphism in general, cementation and 

 metasomatism, contact metamorphism, regional metamorphism, and 

 weathering. The particular subject ap]Dlies to a considerable extent 



