PETROLOGY. 219 



as if roughly turned in a lathe. The rings are thought to be due to 

 slow oxidation of stray particles of iron diffused in a series of gradually 

 enlarging circles. C. E. De R. 



Porte, — . Section of Coal with embedded Crystals. Qicart. Joum. 



Micr. Set. vol. XV. p. 331. 

 Notice of a section of Derbyshire coal which contained a seam of 

 crystalline substance. 



duiroga y Rodrignez, Francisco. El microscopio en litologia. [The 

 Microscope in Lithology.] An. Soc. Espan. Hist. Nat. vol. iv. part 3. 

 Urges the importance of microscopical analysis in lithology. 



. Excupion al Escorial. [Excursion to the Escurial.] An. 



Soc. Espan. Hist. Nat. vol. iv. part 3. 

 Gives results of microscopical analysis of rocks from the neighbourhood. 



Rath, G. vom. Beitrage zur Petrographie. [Contributions to 

 Petrography.] Zeitsch. deutsch. geol. Ges. Heft ii. pp. 295-416 ; 

 2 plates, 13 woodcuts. 



Describes : — I. some rocks from the Andes, with special reference to 

 the triclinic felspars which they contain ; these rocks include the 

 spherolite-lava of Antisana, the dacite of Mojanda, and the andesites 

 of Pululagua, Guagua Pichincha, Tunguragua, and Toluca ; also the 

 obsidian-like andesite of Conejos in Colorado, the trachyte of Per- 

 lenhardt in the Siebengebirge, and the hauyne-lava of Palma in the 

 Canary Islands. II. The rocks of Monzoni ; these are referred to 

 two types described provisionally as ^.ugite-syenite and diabase ; the 

 syenite is a peculiar variety containing orthoclase, plagioclase, and 

 augite ; the diabase is also peculiar, consisting of labradorite, 

 orthoclase, augite, magnesia-mica, hornblende, titanite, magnetite, and 

 pyrite. The Monzoni minerals are fully described ; there is also a 

 description of the melapbyre-dyke of Canzacoli, near Predazzo. III. 

 On a remarkable basalt-dyke near Tannbergsthal in the Saxon Voigt- 

 land. An appendix describes the white ashes of Yulcano ejected on 

 Sept. 7, 1873. F. W. R. 



[Fall of Ashes in Norway.] N. Jahrb. Heft v. pp. 506-517. 



Notes on a shower of volcanic ashes which fell in Norway on March 

 30, 1875, and on recent volcanic eruptions in Iceland, whence the 

 ashes were derived. Analyses of the ashes cited. F. W. R. 



Renard, [Prof. A.]. [Rocks of Belgium.] N. Jahrh. Heft i. pp. 44- 

 46 ; 3 woodcuts. 



There are two large " massives " of quartziferous diorite in the 

 Silurian rocks of Brabant, at Lessinet and at Quenast ; gabbro at 

 Hozemont and near Grand Pre ; some points of quartzose ourite ; about 

 ten occurrences of arkose, regarded by Dumont as eruptive ; and por- 

 phyroidal rocks, some of which the author regards as porphyritic 

 varieties of sericitc-schist, and therefore of clastic origin. F. W. R. 



