PETROLOGICAL ABSTRACTS AND REVIEWS 635 



Moore, E. S. " 'Pele's Tears' and Their Bearing on the Origin 



of Australites," Bull. Geol. Soc. Amer., XXVII (19 16), 51-55. 



Australites are thought to be of volcanic origin since bodies of distinctly 



volcanic origin show that similar forms can originate in the atmosphere from 



rotating liquid bodies. 



Moore, Raymond C. "The Relation of the Buried Granite in 

 Kansas to Oil Production, Bull. Amer. Assoc. Petroleum Geol., 

 IV (1920), 255-61. 



This paper is petrographically of interest from the short description of a 

 buried ridge of granite extending as an elongated mass from north of the 

 Nebraska state line into Kay County, Oklahoma. The ridge reaches its high- 

 est elevation near the north boundary line of Kansas in Nemaha County, where 

 it is less than 500 feet below the surface. It descends gradually to the south 

 and forms a saddle in northwestern Wabaunsee County, then rises in Morris 

 and Chase counties in underground peaks of different elevations. 



O'Harra, Cleophas C. "A BibHography of the Geology and 

 Mining Interests of the Black Hills Region," South Dakota 

 School of Mines Bull., XI, 1917. Pp. 216-17, map i. 



A very important and useful bibliography of the Black Hills, containing not 

 only titles and references, but abstracts of each of the 1,187 items listed. 



OsANN, A. " Der chemische Faktor in einer natiirlichen Klassifika- 

 tion der Eruptivgesteine, I." Ahhandl. d. Heidelberger Akad. 

 d. Wiss., Math.-naturw. KL, Abh. 8, 1919. Pp. 126, pis. 5. 



This is another important contribution to the chemical classification of 

 rocks, and one which will be welcomed by everyone who uses Osann 's system. 

 In former publications the determination of the s, A, C, F, a, c, and/ values, 

 and their plotting in triangular diagrams ended the attempt at classification. 

 Here regular pigeonholes are established, so that it is a very simple matter to 

 locate analyses of similar rocks. The first 23 pages of this work are devoted 

 principally to general discussions and various modifications of the previous 

 methods of calculation. It is to be regretted that nowhere is there given a 

 definite set of revised rules for the computation of the formulae. The various 

 modifications here proposed can be adopted by those already familar with the 

 system, but a beginner will find it necessary to follow the discussion through 

 many pages of print to obtain for himself a workable set of rules. It is true 

 that the system has gradually developed, and various changes have been 

 introduced, but it would seem that it is now in such form that well-defined 

 rules could be given, and it is to be hoped that in the near futvure Professor Osann 



