210 PETROLOGY. 



eruptive rocks of Predazzo; then follows the granite, and next the 

 great group of melaphyrcs and augitic porphyries ; the youngest rock is 

 the red porphyrite. Describes the rocks of Monzoni. F. W. E. 



Doelter, Dr. C. Ueher die mineralogische Zusammensetzung der 

 Mela^ihyre und Augitporphyre Siidost-tirols. [Mineral Composi- 

 tion of S.E. Tyrol Melaphyres and Augite-porphyries.] 3Iin. Mitt. 

 Heft iv. pp. 289-308. 

 The melaphyres of S. E. Tyrol are classed as follows : — 1. Augitic 

 melaphyre : a. Augitic porphyry, or melaphyre rich in augite ; h. Mela- 

 phyres poor in augite, and those containing augite and hornblende. 

 2. Hornblendic melaphyre. 3. Melaphyre free from augite and horn- 

 blende. Plagioclase forms the principal constituent ; orthoclase occurs 

 frequently; the other constituents are augite, uralite, hornblende, 

 olivine, and magnetite, frequently titaniferous. As secondary forma- 

 tions there are calcite, epidote, delessite, and chalcedony. F. W. R. 

 Doelter, Dr. C, and Dr. R. Hoernes. Chemisch-genetische Betrach- 

 tungen iiber Dolomit. [Chemical Origin of Dolomite.] Jahrh. 

 h.-h. geol. Riichs. Bd. xxv. Heft 3, pp. 293-332. 

 Treats first of the literature of former experiments and theories on 

 dolomitization. Describes the S. Tyrolese Dolomites. Examples from 

 many horizons in the Alpine Trias are described, with analyses. Some 

 conclusions as to the genesis of dolomite are then drawn. Limestones 

 poor in magnesia are held to have been probably formed direct by 

 organic agency, as some living corals contain magnesia. Metamorphosis 

 by later introduction of magnesia- carbon ate could only affect some 

 portions, and not large rock-masses. Rocks rich in magnesia possibly 

 resulted from the action of magnesium-chloride on organically formed 

 rock, soon after its deposition. The amount of magnesia may be con- 

 centrated by subsequent dissolving out of lime, which is more soluble in 

 carbonated waters. E. B. T. 



Durand-Claye, Leon. [Analyses of Limestone.] Rev. Geol. t. xii. 



pp. 47, 48. 

 Twelve analyses are given of four beds of limestone from the Lower 

 Cretaceous of the Homme-d'Armes quarry, north of Montelimart 

 (Drome). Also eighteen analyses of limestone from Cruas (Ardeche), 

 and the mean composition of limestones from three other quarries in 

 the Rhone valley. G. A. L. 



. [Analysis of Limestone from Ablancourt (Marne).] Rev. 



Geol. t. xii. p. 50. 

 Five analyses given. 



. [Analysis of calcareous sand from Somma Bay.] Ibid. p. bQ. 



Ebray, Th. Quelques remarques sur les Granulites et les Minettes ; 



nouvelle classification des roches eruptives. [Granulites and 



Minettes; New Classification of Erui)tive Eocks.] Bull. Soc. Geol. 



France, 3 scr. t. iii. pp. 287-291. 



Denounces the use of inineralogical terms applied to eruptive rocks 



in discussing geological questions. Proposes a classification of such 



