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NATURE 



[July 21, 192 1 



professional reader, require a little criticism for 

 the benefit of the layman in these matters. 



Dr. Hollander, like all enthusiasts, is in- 

 clined to lay the onus of failure of vision on 

 those who do not agree with him. He disposes of 

 his opponents on the ground that they do not 

 follow out his system ; but he must realise that 

 some of the greatest intellects in science have 

 beeft busy on these problems, and that they cannot 

 all be wrong and only he be right. He must give 

 a little credit to the labours of such men as Sir 

 Frederick Mott, Sir Victor Horsley, and 

 many others one might mention. Again, the diffi- 

 culty the physicians of our mental hospitals have 

 to face is not the fact that they are not allowed to 

 fulfil their duty — they have every opportunity to 

 do that in the very efficient and well-equipped 

 modern mental hospital — but the attitude of the 

 friends and relatives of the mental patient who, 

 for sentimental reasons, oppose any effort to place 

 the patient under proper care in the early stages 

 of the disorder. As regards the question of treat- 

 ment, of course everyone is entitled to whatever 

 opinion he chooses, but it may be as well to point 

 out that the consensus of modern opinion is that 

 the day has not yet dawned when mental 

 disorder can be treated by the surgeon. In 

 a few cases of very definite brain injury 

 an operation might be considered, but, even so, 

 it is often found that the patient's last state is no 

 better than the first. 



Space does not permit of any detailed criticism 

 of the remaining chapters of the book ; it must 

 suffice to say that the author passes on from 

 criminology to thought reading and allied sub- 

 jects, and ends upon a metaphysical note. 

 The book is well written and well arranged ; 

 every credit must be given for the truly im- 

 mense labour involved in its compilation ; but 

 it is to be feared that it is too much out of joint 

 with the times to exercise much effect on the 

 opinion of the day on these matters. 



Mineralogy for Students. 



(i) Economic Mineralogy: A Practical Guide to 

 the Study of Useful Minerals. By T. Crook. 

 Pp. xi + 492. (London: Longmans, Green, and 

 Co., 1921.) 255. net. 



(2) Mineralogy : An Introduction to the Study of 

 Minerals and Crystals. By Prof. E. H. Kraus 

 and Dr. W. F. Hunt. Pp. xiv+561. (New 

 York and London: McGraw-Hill Book Co., 

 Inc., 1920.) 2";^$. 



EACH of these books is intended both as a 

 text-book for students and as a work of 

 reference for practical men. 

 NO. 2699, VOL. 107] 



(i) In Mr. Crook's case the reader has the 

 advantage of his life-long employment on the 

 economic investigation of minerals, while his ex- 

 perience as a lecturer enables him to appreciate 

 the difficulties of the beginner. He carefully 

 avoids unnecessary excursions into theoretical con- 

 siderations, but his explanations, so far as they 

 extend, are exceptionally clear and simple. He 

 gives considerable attention to the optical exam- 

 ination of crystals, on account of its value in 

 recognising minerals ; and there is a helpful 

 chapter on the use of the blowpipe and chemical 

 methods generally. Another chapter is concerned 

 with the physical analysis of crushed rocks and 

 loose detrital sediments, a subject that the author 

 has made peculiarly his own ; and the short 

 account of the geology of mineral deposits should 

 be of use to the prospector. 



The greater [Sortion of the book is, however,, 

 devoted to a detailed description of the minerals of 

 practical importance. The arrangement and treat- 

 ment are frankly based on economic considera- 

 tions, which should be a recommendation to all 

 who are engaged in the commercial development 

 of mineral resources. Moreover, Mr. Crook does 

 not confine his attention to minerals in the strictly 

 scientific meaning of the word, but includes all that 

 is covered by the legal and technical definition of 

 the term — everything which is mined for its 

 economic value — so that coal, asphalt, and 

 petroleum find their place in his survey. He also 

 deals briefly with building materials and road 

 metal. The volume concludes with some useful 

 determinative tables, which are set out in such 

 a manner that it is possible to glance rapidly 

 through them in search of the information re- 

 quired. The text is illustrated by clear diagrams, 

 and by excellent photographs of minerals taken by 

 the author himself. 



(2) Prof. Kraus and Dr. Hunt present us with a 

 treatise of a somewhat more elaborate character, 

 largely compiled from previous publications of 

 one or both of the authors. Considerable atten- 

 tion is devoted to crystallography, and there are 

 detailed tables for determining minerals. In the 

 general description of the commoner minerals 

 they are arranged according to the usual 

 chemical classification, but there is a separate 

 chapter on gem-stones, and another in which the 

 minerals are classified according to the elements 

 to which they owe their economic value. Monazite, 

 however, appears in this section under cerium, 

 which, although present in considerable amount, is 

 of little commercial importance, instead of under 

 thorium, for which it is almost exclusively 

 worked. The use of tetra- (instead of tetarto-) 

 in referring to a quarter-pyramid in the triclinic 



