582 PETROLOGICAL ABSTRACTS AND REVIEWS 



Three types of picrite are distinguished according to texture: (i) hypi- 

 diomorphic-granular (all the analyzed specimens belong to this group); 

 (2) holocrystalline-porphyritic rocks with hypidiomorphic-granular ground- 

 masses; and (3) hypocrystalline-porphyritic rocks with intersertal ground- 

 masses. 



Since such different textures are included among the picrites, the 

 author proposes for the third type, from its occurrence at Altschonfels, the 

 name of "Schonfelsit." In composition, Schonfelsite is a porphyry with 

 closely crowded phenocrysts (persemic) of olivine and augite in a mega- 

 scopically aphanitic ground-mass. Microscopically this ground-mass is 

 seen to consist of rare apatite, aggregates of titaniferous magnetite, granular 

 augite, long prismatic crystals of bronzite, automorphic laths of bytownite- 

 anorthite (sometimes anorthite), and a gray or brown devitrified basis. 

 The occurrence of basis in picrite is noteworthy and points to the effusive 

 nature of the occurrence. This basis fills the interstices between the 

 divergent laths of feldspar and also occurs between the pyroxene grains as 

 a distinct interstitial filling. It is completely made up of fine scaly particles 

 of a chloritic aggregate in which there still remain well-preserved trichites 

 and globulites. 



There are numerous secondary minerals found in the picrites described. 

 They are tremolite, uralite, antigorite, bastite, pseudophite, pennine, 

 delessite, prochlorite, talc, dolomite, siderite, epidote, kaolin-like products, 

 and magnetite. Albert Johannsen 



TuTTON, A. E. H., Crystalline Structure and Chemical Constitution. 

 London: Macmillan, 1910. Pp. viii-l-200, figs. 54. $1.50 net. 



The title of this book is perhaps a little misleading, as it is not a general 

 treatise on the subject, but is rather, as is stated in the Preface, an effort 

 to present in a concise manner the author's original contributions to the 

 subject of the relation between the form, structure, and physical properties 

 on the one hand, and the chemical composition of the substances on the 

 other. 



The first four chapters are devoted to a historical sketch by way of 

 introduction. The Hatiy-Mitscherlich controversy on isomorphism is 

 reviewed in its relation to more views on the subject. Iti a discussion of 

 the periodic classification of the elements in its relation to isomorphism, 

 the author digresses for a moment to decry the growing usage of oxygen = 

 16 instead of hydrogen = 1 as a basis for atomic weights. His reasons 

 seem to be sentimental rather than practical, as chemists in general are 

 agreed as to the advantages of the former. 



