SEPTEMBER 7, 1906.] 



SCIENCE. 



301 



One may even abandon hope of and desire 

 for the equalization of intellect and still keep 

 the essence of Professor Ward's optimism. 

 For every one of the desirable consequences 

 of the equalization of intellect may be gained 

 as well, if not better, by the same amount of 

 effort and wisdom directed toward its increase. 

 Space is lacking for me to defend this some- 

 what rash amendment, which the author would 

 probably repudiate. 



Edward L. Thorndike. 

 Teachers College, Columbia University. 



Geometrische Kristallographie. By Ernst 

 SoMMERFELDT, Privatdoccnt an der Univer- 

 sitat. Tiibingen. Pp. vi + 139, 31 plates 

 and 69 text figures. Leipzig, W. Engel- 

 mann. 1906. 



This is a book intended for advanced stu- 

 dents of crystallography, written from the 

 standpoint of the mathematician. Specifically 

 limiting himself to the purely geometrical 

 properties of crystal solids, the author de- 

 velops his theme from the definitions of sym- 

 metry and in the first chapters defines the 

 thirty-two recognized classes of crystals dis- 

 tinguished by varying grades of symmetry. 

 These groups are variously classified and ad- 

 mirably illustrated by the plates which give 

 for each of the classes the possible crystal 

 forms and show very graphically the rela- 

 tions between them. In the following chapters 

 the mathematical relations existing between 

 the faces of the crystal are deduced and the 

 fundamental crystallographic laws are stated. 

 The mathematical processes, particularly vec- 

 tor analysis and the properties of deter- 

 minants, which are chiefly involved are made 

 the subject of a special chapter and their 

 treatnaent is stated by the author to be original 

 and to have an interest quite aside from the 

 application to the problems of this work. 



To the student actually engaged in the meas- 

 urement and study of crystals the book offers 

 little of practical interest except in the pre- 

 sentation of formulae for the transformation 

 of indices and axes which are here developed 

 in very general form. 



Charles Palache. 



SCIENTIFIC JOURNALS AND ARTICLES. 

 The contents of the American Journal of 

 Science for September are as follows: 



R. A. Daly: 'Abyssal Igneous Injection as a 

 Causal Condition and as an Effect of Mountain- 

 building.' 



W. E. Ford : ' Some Interesting Beryl Crystals 

 and their Associations.' 



F. E. Weight: ' ScMstosity by Crystallization: 

 A Qualitative Proof.' 



M. R. Campbell: 'Fractured Bowlders in Con- 

 glomerate.' 



E. L. Furlong : ' Exploration of Samwel Cave.' 



T. L. Watson : ' Occurrences of Unakite in a 

 New Locality in Virginia.' 



E. H. Sellards : ' Types of Permian Insects.' 

 R. H. Ashley : ' Analysis of Dithionic Acid and 



the Dithionates.' 



The American Journal of Anatomy, Vol. 

 v.. No. 4, September 1, 1906, contains the 

 following articles: 



R. B. Bean : ' Some Racial Peculiarities of the 

 Negro Brain.' (With 8 tables, 16 figures and 12 

 charts. ) 



F. P. Mall: 'On Ossification Centers in Hu- 

 man Embryos.' (With 6 tables and 6 figures.) 



J. L. Bremer : ' Description of a 4 mm. Human 

 Embryo.' (With 16 figures.) 



Charles R. Stockard : ' The Development of 

 the Mouth and Gills in Bdellostoma.' (With 36 

 figures. ) 



The July number of the Journal of Mathe- 

 matics contains the following articles : 



Edward Kasner : ' The Geometry of Differ- 

 ential Elements of the Second Order with respect 

 to the Group of all Point Transformations.' 



F. J. B. Cordeiro : ' Gyroscopes and Cyclones.' 



W. A. Manning : ' On the Primitive Groups of 

 Class Ten.' 



Virgil Snyder : ' On Certain Unicursal Twisted 

 Curves.' 



Henry Livingston Coar : ' Functions of Three 

 Real Independent Variables.' 



DISCUSSION AND CORRESPONDENCE. 

 THE NATURE AND ORIGIN OF VOLCANIC HEAT. 



In Science for August 10 Dr. Elihu Thom- 

 son gives a theory of volcanic energy which 

 he correctly describes as an extension of the 

 ideas of Mallet. Having been recently much 

 occupied with the theory of volcanoes in con- 



