Geology and Mineralogy. 467 



the volume is taken up with petrographical research, the author's 

 own particular field of inquiry, which gives an interesting and 

 most important vista into the theory of the formation of quartzitic 

 rocks and the occurrence of free quartz in volcanic magmas. 



Angelo Heilprin. 

 Philadelphia, April 22, 1905. 



14. Hecherches geologiques et petrographiques sar P (Jural du 

 Nord ; par L. Duparc et F. Pearce. Mem. Soc. Phys. d'Hist. 

 Nat. Geneve, vol. 34, fas. 5, pp. 383-602. Pis. and map. 1905. — 

 The first portion of this work was published in 1902 (ibidem, pp. 

 57-218) and gave a general description of the portion of the 

 region in the Urals which had been studied (Rastesskaya and 

 Kizelowskaya-Datcha, Govern. Perm.) Different parts of the 

 area were then taken up in detail, the geology described and the 

 petrography of the igneous rock formations presented, accom- 

 panied by numerous analyses. In the second memoir these de- 

 tailed descriptions are continued, studies of the crystalline schists 

 are also given, and the work concludes with observations on the 

 structural geology and summations of the results obtained. 



The chief interest centers on the masses of igneous rocks which 

 have been investigated in the field and laboratory ; they are 

 chiefly of basic ferro-magnesian types, gabbros, dunites and 

 pyroxenites. Of the latter a special type is described consisting 

 of a foliated pyroxene with a variable amount of olivine and 

 magnetite ; the texture is granitic ; the magnetite, playing the 

 same role as quartz in a granite, forms the cement to the other 

 minerals. To this rock the name of koswite is given. To another 

 typ e which contains a certain amount of feldspar rich in lime, 

 but which differs chemically from the gabbros, the name of tilaite 

 is given. 



The work is enriched by many figures and half-tones in the 

 text, and is not only an important and valuable contribution to 

 our knowledge of the Urals, but contains much in addition that 

 is. of general interest to geologists and petrographers l. v. p. 



15. Einleitung in die ehemische Krystallographie ; von P. 

 Groth. Pp. 80, 8vo. Leipzig, 1904 (Wilhelm Engelmann). — 

 The author of this little volume has made so many important con- 

 tributions to the subjects of Mineralogy and Crystallography, 

 both separately and in their mutual relations, that it will not be a 

 matter of surprise that the present volume, although brief in 

 extent, is very helpful and suggestive in regard to the various 

 topics it discusses. Its object, briefly stated, is to present the 

 relations which exist between the properties of crystallized bodies 

 and their chemical constitution as based upon a definite theory as 

 to the structure of crystals. It is, moreover, introductory to an 

 exhaustive work in preparation by the author, in which it is pro- 

 posed to give a systematic and critical presentation of crystal 

 forms and the physical properties of crystallized substances. 



16. Grundzuge der Krystallographie ; von Prof. C. M. Viola. 

 Pp. x, 389, 8vo. Leipzig, 1904 (Wilhelm Engelmann).— This 



