206 PETROLOGY. 



chlorite. Thus, although hornblende may occur as an accessory, the 

 rock ought to be regarded as a felstone -porphyry, or '-'■ porphyrite,^^ 

 not as a greenstone-porphyry. The author gives details as to the micro- 

 scopic characteristics of each mineral. E. T. H. 



Hull, Prof. E. On the Microscopic Structure of a Granitoid Quartz- 

 porphyry from Galway. Monthly Mic. Journ. no. 61, pp. 11-13, 

 with part of plate. 

 Describes the structure of a rock near Salt Hill, S. "W. of Galway. It 

 has the constituents of a granite ; but the base is felspathic, not sili- 

 ceous, and the rock is therefore a quartz-porphyry rather than a true 

 granite. F. "W. B. 



. Microscopic Structure of Basalt of Ballyleny. See p. 11. 



. Microscopical Notes. Memoir on sheets 76, 77, Geological 



Survey, Ireland. See p. 40. 



Hunt, Dr. T. S. Eemarks on Prof. Newberry's paper on *^ Circles 

 of Deposition," &c. (p. 124). Proc. Amer. Assoc, vol. xxii. B, 

 p. 196. 

 Reminds readers that twelve years ago he announced, on chemical 

 grounds, that all magnesian limestones had been formed by the simul- 

 taneous precipitation of carbonate of lime and magnesia from solutions 

 concentrated by evaporation. A. H. G. 



. La Chimie de la Terre. [The Chemistry of the Earth.] 



Rev. Univ. des Mines, t. xxxvi. pp. 246-295. 



Translated from the Smithsonian Report for 1869. On the last page 

 are some additional observations by the author. According to him, it 

 is the decomposition of the crystalline rocks in ancient times which 

 has been the source of all the clays of the non- crystalline rocks; and 

 the alkalies set free during this decomposition have given rise, by their 

 reaction on the waters of the ocean, to the carbonates of lime and 

 magnesia of those rocks. In glaciated countries the crystalline rocks 

 have suffered no decomposition since the glacial erosion; in non- 

 glaciated countries these rocks are deeply decomposed. G. A. L. 



Jannettaz, E. Note sur les mineraux et les roches recueillies dans 

 I'Alaska et les lies Aleoutiennes, par M. A. Pinart. [Minerals 

 and rock-specimens from Alaska and the Aleutian Islands.] Bull. 

 Soc. Geol. Prance, 3 ser. t. ii. pp. 122-125. 



A descriptive catalogue of a small collection of minerals and rocks. 



Les Roches. Description deleurs elements : methode de deter- 



mination. Pp. viii, 285. 16mo. Paris (39 woodcuts). 



John, K. Analyse eines Augit-Hornblende-Andesits von Toplitia 

 bei Gyorgy St. Miklos in Siebenbiirgen. [Analysis of an augitic 



