PETROLOGICAL ABSTRACTS AND REVIEWS 439 



The universal stage in this instrument, however, is considerably larger 

 than in the detachable stage, being capable of taking sections 28X48 

 mm., thus doing away with the necessity of using circular sections. 



A. J. 



Loewinson-Lessing, F. "Beitrage zur Systematik der Eruptiv- 

 gesteine, I." Tire d. Ann. d. Inst. Polyt. Pierre le Grand a St. 

 Peter shourg, XV (191 1), 229-43. 



After a period of ten years, the author resumes his critical studies on 

 the nomenclature and classification of igneous rocks, and proposes to 

 issue a continuation of his former series of papers which was published 

 in Tschermak's Mittheilungen in 1 889-1 902. The paper here reviewed is 

 the first of the new series, unfortunately printed in the Russian language 

 and consequently unavailable, except so far as the short resume in 

 German goes, to the majority of the petrologists in this country. 



The writer discusses first the transition members of the effusive rocks 

 between those from the alkali and from the alkali-earth magmas, and 

 second, the absence of mono-mineral rocks among the effusives. He 

 believes this absence to be a proof that the formation of eutectic and 

 mono-mineral differentiation rocks takes place only in deep-seated 

 magmas. That they do not reach the surface as effusives he thinks may 

 be due to their viscosity and high melting-point, or that they are more 

 active in assimilating the country rocks and, therefore, in the course of 

 their eruption, always become changed in composition. 



Albert Johannsen 



LouDERBACK, George Davis. "The Monterey Series in Cali- 

 fornia," Bull. Dept. Geol. Univ. Cat., VII (1913), 177-241. 



LouGHLiN, G. F. "Contribution to the Geology of the Boston and 



Norfolk Basins, Massachusetts. I. The Structural Relations 



between the Quincy Granite and the Adjacent Sedimentary 



Formations," Amer. Jour. Sci., XXXII (1911), 17-32. 



The igneous rocks in the area studied include an altered biotite 



granite series, an older felsite series, the Quincy alkaline granite series, 



and alkaline felsite. The sediments are much folded and include the 



conglomerates, sandstones, and slates of the Boston and Norfolk basins. 



A. J. 



