NATURE 



385 



THURSDAY, FEBRUARY 23, iJ 



THE NEW MINERALOGY. 



A Text- Book of Mineralogy J- with an Extended Treatise 

 on Crystallography and Physical Mineralogy . By 

 Edward Salisbury Dana. New edition, entirely re- 

 written and enlarged, with nearly 1000 Figures and a 

 Coloured Plate. Pp. vii + 592. (New York : John 

 Wiley and Sons. London : Chapman and Hall, 

 Ltd., 1898.) 



Manual of Determinative Mineralogy ; with an Intro- 

 duction on Blowpipe Analysis. By George J. Brush. 

 Revised and enlarged, with entirely new Tables for the 

 Identification of Minerals, by Samuel L. Penfield. 

 Fifteenth edition. Pp. x + 312. (New York : John 

 Wiley and Sons. London : Chapman and Hall, 

 Ltd., 1898.) 



Elemente der Mineralogic, hegriindet von Carl Friedrich 

 Natcmann (i873t). Dreizehnte VoUstandig umge- 

 arbeitete Auflage von Dr. Ferdinand Zirkel. II. Halfte : 

 Specialler Theil. (Leipzig: W. Engleniann. London: 



" Williams and Norgate, 1898.) 



THIRTY years ago the science of chemistry passed 

 through a great revolution ; new points of view 

 were occupied by some investigators, and fresh lines of 

 inquiry opened up by others ; a general revision of the 

 nomenclature and notation of the science became neces- 

 sary, and thus arose what has been called " the New 

 Chemistry." The last few years has witnessed a similar 

 crisis in the history of mineralogy ; crystallography has 

 been reconstructed on a revised basis, and new views 

 concerning the optical properties of crystals have rendered 

 much of the old terminology of the science obsolete if not 

 actually misleading. 



It is a fortunate circumstance for English-speaking 

 students and teachers of the subject that, in the first two 

 volumes placed at the head of this article, we have a 

 presentation of the science of mineralogy, in its modern 

 aspects, which leaves little to be desired in the way of 

 simplicity, precision and completeness. Prof. E. S. Dana, 

 who is Professor of Physics as well as Curator of Minera- 

 logy in the Yale University, gave the world in the year 

 1877 his "Text-Book of Mineralogy" — a very admirable 

 introduction to the science. But as time passed on, and 

 new methods of inquiry were invented, or old ones became 

 obsolete, the necessary modifications and interpolations 

 in the te.xt of the book, when successive editions were 

 called for, could not fail to mar the symmetry, and to 

 some extent destroy the value of the work as a scientific 

 treatise. Now the whole book has been rewritten, and, 

 as its author is equally familiar with the methods and 

 literature of physics, as well as with the technicalities and 

 nomenclature of mineralogists — and these are by no 

 means always in harmony with one another — a book has 

 been produced which may be confidently recommended 

 alike to students of the physical and the natural sciences. 

 Prof. S. L. Penfield, the Professor of Mineralogy in the 

 Sheffield Scientific School of the Yale University, has 

 similarly rewritten the well-known " Manual of Determin- 

 ative Mineralogy, with an Introduction on Blowpipe 

 Analysis," of Prof. G. J. Brush — a work which first 

 NO. 1530, VOL. 59] 



appeared in 1874, and since that date has passed through 

 no less than fourteen editions. It is not too much to say 

 that, wherever determinative mineralogy has been taught 

 to English-speaking students, the work of Brush has been 

 adopted as by far the best and most thorough guide to 

 the subject. Originally based on Von Kobell's "Tafeln 

 zur Bestimmung der Mineralien," successive additions 

 and corrections have given the work a character of its 

 own ; and without in any way impairing the efficiency or 

 destroying the familiar features of the work. Prof. Pen- 

 field has brought the book up to date, and at the same 

 time added much new matter which will be regarded by 

 all teachers of the subject as being remarkable alike for 

 lucidity and masterly treatment. 



It is in the treatment of the difficult subject of crystal- 

 lography that teachers and students will first appeal to 

 these works for guidance at the present time : and they 

 will not appeal in vain. During the last decade the six 

 systems of crystallography have undergone complete 

 disintegration ; and an entirely new nomenclature has 

 become necessary, in order to adequately express the 

 great facts of isomorphism, heteromorphism, and of 

 crystal-symmetry generally. The mathematical researhes 

 of Sohncke, Wulff, Schonfliess, Federow, Barlow and 

 others have shown that there are thirty-two — and only 

 thirty-two — modes of molecular grouping possible in 

 crystals ; and, of these, exemplifications of all but three 

 have already been observed, either among artificially 

 crystallised salts or among natural minerals. The great 

 majority of minerals crystallise in one or other of some 

 eight or nine of these groups, however ; while only five 

 or six other groups are at all commonly represented 

 among the rarer species of the mineral kingdom. It is to 

 these groups then, and not to the more comprehensive 

 systems of the crystallographer, that the attention of 

 students of practical mineralogy must in future be 

 directed ; and we are indebted to Profs. Dana and Pen- 

 field for a simplification of the very cumbrous nomen- 

 clature hitherto adopted for the crystal groups. It is a 

 distinct gain to speak of the " Pyrite-type " rather than 

 of " pyritohedral-hemihedral forms " of the Isometric 

 system, and of the " Quartz-type " rather than of ' trapezo- 

 hedral-tetartohedral forms" of the Rhombohedral system. 



The complicated mathematical questions involved in 

 the derivation of hemihedral, tetartohedral and hemi- 

 morphic forms from holohedral ones, now lose much of 

 their importance to the practical crystallographer. As 

 Prof. Dana says : 



" The development of the various possible kinds of 

 hemihedral (and tetartohedral) forms under a given 

 system has played a prominent part in the crystallography 

 of the past, but it leads to much complexity and is dis- 

 tinctly less simple than the direct statement of the 

 symmetry in each case. The latter method is sys- 

 tematically followed in this work ; and the subject of 

 hemihedrism is dismissed with the brief (and incomplete) 

 statements of this and the following paragraphs." 



Students of the subject familiar with the methods of 

 older treatises on crystallography, will find that Prof. 

 Dana has been able— while giving an admirably clear and 

 complete account of crystallographic methods and results 

 in 144 pages of his book— to dismiss the subjects referred 

 to in less than a single page. 



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