214 PHTEOIOGY. 



tuent minerals in lavas of Vesuvius (see p, 207). Doubts the sufficiency 

 of the method. E. B. T. 



Roth, J. Ueber die Wirkung verdunnter Essigsaure auf dolomitischo 

 Kalko. [Action of Dilute Acetic Acid on Dolomitic Limestone.] 

 Min. Mitth. Heft i. p. 69. 



Calculates the composition of a given dolomitic limestone by the 

 quantity dissolved out by acetic acid. 



Eutley, Frank. On the Microscopic Characters of some Eruptive 



Bocks from Somersetshire and Gloucestershire. [Appendix to 



"Woodward's Memoir on the Geology of East Somerset, &c. (see 



p. 42). Pp. 208-212, plates v.-ix.] 



Describes the microscopic structure of 7 specimens of the igneous 



rocks of this district ; they are, as a rule, highly altered. One is a " fel- 



stone containing much magnetite and a little hornblende ; " another a 



devitrified porphyritic pitchstone ; the others are dolerites or basalts, 



in one of which fragments of porcellanite are entangled. T. G. B. 



. On some Structures in Obsidian, Perlite, and Leucite. Ilicr. 



Journ. vol. xv. pp. 176-183 ; 2 plates. 

 The microscopic structure of sections of these rocks having been 

 described and compared, the conclusion is drawn that there is a close 

 relationship between certain of their structures. Analyses are given of 

 obsidian from Lipari, and of leucite from Vesuvius. Of the spherulitic 

 obsidian the author says, " To my mind we have here not merely a 

 microscopic section, but a geological section of considerable significance, 

 .... and we have here a somewhat correct rendering, I believe, of the 

 way in which many great geological phenomena have taken place." 



E. T. N. 

 Sauer, G. A. Untersuchungen iiber phonolithische Gesteine der 

 Canarischen Inseln. [Phonolites of the Canary Islands.] Zeitsch. 

 gesammt. Nat. n. P. Bd. xiii. pp. 303-365, pi. v. 

 Describes sanidine, orthoclase, hornblende, augite, hauyne, and 

 nosean, nepheline, mica, chlorite, titanite, apatite, magnetic and titan- 

 iron, giving several analyses. The phonolites yielding these are divided 

 into felspar-, nephelin-, hauyne-, and nosean-phonolites. W. H. D. 



Schmid, E. E. Die Kaoline des thiiringischen Buntsandsteins. 

 [Porcelain-clay in Thuringian Trias.] Zeitsch. deutscli. geol. Ges. 

 Bd. xxviii. Heft i. pp. 87-110 ; 6 woodcuts. 

 The Thuringian porcelain- clays belong mostly to the Middle Bunter 

 Sandstone ; they contain quartz-granules to the extent of 6-26 p. c, 

 with microscopic plates of mica, schorl, &c. They are classed there- 

 fore as kaolinito rather than pure kaolin, and are of secondary origin. 

 Many analyses given. The chief localities are Eisenberg, Osterfield, 

 and Kmenau. E. B. T. 



. [Ilmenau Porphyrites.] Zeitsch. deutscli. geol. Ges, Bd. xxviii. 



Heft 3; pp. 640-643. 



