PETROLOGY. 203 



W. Keiss described some hypcrsthenitcs occurring with diabase in 

 the Island of Palma, where thoy form a lower or diabase-group partly 

 overlain by a younger of lava-formation. These so-called hj'persthenites 

 contain no hypersthcno, but are in different specimens diabase, diorite, 

 and syenite. P. W. li. 



Collins, J. H. On the China Clay and China Stone of Devon and 

 Cornwall. Jonni. Soc. Arts, vol. xxiv. no. 1224, pp. 565-572. 



A bibliography of the subject given ; the modes of occurrence and of 

 working described ; and the uses of the clay and of debris noticed. The 

 decomposed parts of the granite are associated with veins of tourmaline 

 and other minerals containing fluorine ; and the author thinks that tho 

 decomposition has been caused by fluorine, ttc, coming up from below, 

 not by carbonic acid and water from above. Decomposition is more 

 general at the junction of granite with other rocks than elsewhere. 

 The clay-rock is mostly covered by a layer of stones, sand, or impure 

 clay, up to 40 feet thick. Decomposed granite is found at all levels 

 but tho highest points. W. W, 



Cossa, Prof. Alfonso. Iliccrche di Chimica Mineralogica sulla Sienito 



del Biellese. [Chemico-raineralogical Examination of the Syenite 



of tho Biellese.] Mem. li. Ac, Sci, Torino, ser. 2, t. xxviii. pp. 



309-337. 



Gives density, anal3'sis, and crystallographic description of the ortho- 



clase and hornblende, a general analysis of the syenite, and the result 



of the action on it of chemical solutions. AV. H. D. 



Dathe, Dr. E. Olivinfels, Serpentine und Eklogitc des siichsischcn 

 Granulitgebietes. Ein Beitrag zur Petrographie. [Olivine-rock, 

 Serpentine, and Eclogito of the Granulite District of Saxony.] 

 N. Jahrh. Heft iii. pp. 225-249 ; Heft iv. pp. 337-351. 

 An inquiry into the origin of the Saxon serpentine. Olivine-rock 

 has been found in three places : at Hciersdorf and Mohsdorf it is a 

 garnct-olivine-rock, while at llussdorf it is an enstatite-bearing variety ; 

 each occurrence is described in detail. Two varieties of Saxon serpen- 

 tine are recognized, and their occurrence described ; one is characterized 

 by the presence of garnet, the other by that of a mineral belonging to 

 the enstatito group. Believes that the garnet-serpentine has been 

 derived from the garnctiferous variety of olivine-rock, while tho bron- 

 zite-serpentine is referred to the alteration of tho enstatite-rock. 

 Describes the occurrence of eclogito, and discusses its relations with 

 serpentine. Concludes, however, that eclogito has not contributed to 

 the formation of serpentine in the district. F. W. 11. 



Daubree, Prof. — . Observations sur un nouvcl exemple des decom- 

 positions chimiques qui s'operent journellement dans les silicates, 

 iiotamment dans le feldspath. [New Instance of the Chemical 

 Decomposition daily taking place in Silicates, especially in Felspar.] 

 Bull. iSoc. Ayric. France, t. xxxvi. p. 508. 



