520 Revieics — L. V. Pirsson — Rocks and Minerals. 



the proper method of working one, and so on. It, however, by no 

 means consists of a series of working notes briefly and badly set 

 down, but opens with a short, yet sufficiently general, account of 

 geological formation and the origin of ore which will enable the 

 miner who has had no previous geological training to appreciate the 

 disposition of lodes and the natural processes that have brought them 

 about. The general reader, moreover, will be interested in the 

 statistical accounts of the mineral resources of the country which are 

 incidentally given; there seems no doubt that, despite a somewhat 

 chequered career in the past, the mineral industry of Rhodesia has 

 a great future to be realised when the country has been opened up 

 and the railway facilities fully developed. 



After the general discussion referred to, chapters follow which deal 

 with the metals, precious and base, and the minerals containing them, 

 precious stones, and coal. It may surprise many to find that Rhodesia 

 already ranks as one of the great gold-producing countries of the 

 world, and may in the near future challenge the position held by the 

 Transvaal. The account of the methods used by the natives in 

 ancient times for crushing and concentrating the ores shows how little 

 in principle the system of working has altered. The section dealing 

 with zinc includes a description of the remarkable mineral occurrence 

 at the new Broken Hill mines which has attracted so much attention 

 among mineralogists. The Somabula gem-district appears to be 

 prolific in all kinds of precious stones, especially diamond, chrysoberyl, 

 and topaz,, the last of a peculiar pale-blue colour. Rhodesia is 

 fortunate in possessing an ample coal supply, which will be of 

 increasing importance as time goes by and local manufacturies 

 spring up. 



The book is well printed and enriched by a large number of 

 excellent illustrations, mostly reproduced from photographs. 



III. — Rocks and Rock Minerals. A Manual of the Elements of 

 Peteology without the use of the Microscope. By Louis V. 

 Pirsson. pp. 414 -fvi, with 74 figures in the text and 36 plates. 

 New York, John Wiley & Sons; London, Chapman & Hall, 1908. 



SO great was the impetus imparted to the development of petro- 

 logical science by the introduction of the use of the polarising 

 microscope that all modern textbooks dealing with the study of 

 rocks consider the subject from the microscopical point of view. Yet 

 there has long been felt the need for a book that should enable an 

 observer by the aid of a pocket-lens and the application of a few 

 simple tests, which can readily be carried out even in the field, to 

 identify with sufficient accuracy for practical pui-poses any rock that 

 may be met vi'ith. Thus the engineer and the architect are anxious 

 to learn whether some particular rock is characterised by strength 

 and durability, and are not concerned with the minutiae of petrology. 

 There can be little doubt that Professor Pirsson's manual will be in 

 great demand ; of the excellence of the work his name alone is 

 sufficient guarantee, and he has had the teaching experience requisite 

 for gauging the type of book wanted. 



