684 ABSTRACTS OF PAPERS 



Fayette and Greene counties, Pennsylvania, was also overlooked by the geolo- 

 gists of the first Geological Survey of Pennsylvania, as well as by those of the 

 Second Survey of that State, and finally by those of the United States Geo- 

 logical Survey, who. under Mr. M. R. Campbell's supervision, covered the area 

 described in the Uniontown-Masontown Folio with much more detailed studies 

 than either of the former surveys. It remained for the entry of a coal com- 

 pany to run up against this almost impenetrable wall of igneous rock, nearly 

 20 feet thick, before the geologists learned of the presence of this dike, which 

 Mr. Hice states can now be traced westward across the Monongahela River 

 into Greene County from the locality of its first discovery in the Masontown 

 coal field of Fayette County. 



LAVAS OF HAWAII AND THEIR RELATIONS 

 BY WHITMAN CROSS 



(Abstract) 



The Hawaiian Islands, using the term in its comprehensive sense, form a 

 particularly well defined petrographic province. Their lavas are clearly co- 

 magma tic. A review of the known varieties of these lavas brings out several 

 points of interest in current petrological discussion. 



While basalt of a common type is the predominant rock of the islands there 

 is a much greater variety than is commonly supposed. The range of known 

 rocks is reviewed. Chemical characters are discussed on the basis of thirty- 

 nine existing analyses, showing many of the rocks to be of so-called alkaline 

 types. 



The relations of the magmas as differentiation products are compared with 

 those of other island groups of the Pacific Ocean, and the distribution of the 

 Hawaiian types in other parts of the world is considered. 



It is shown that the distinction between the "Atlantic and Pacific branches" 

 of igneous rocks is highly fallacious as regards both geographic distribution 

 and genetic relations. 



PRODUCTIOX OF APPARENT DIORITE BY METAMORPHISM 

 BY ARTHUR KEITH 



(Abstract) 



In the southern Appalachians there is a group of rocks with the composition 

 of diorite and the noncrystalline texture of a plutonic rock. These have been 

 described by various authors as "quartz diorite" and an igneous origin has been 

 attributed to them. Objections to such an assignment have been known from 

 the first discovery of the rock, prime among them being its habit of grading 

 into the inclosing sedimentary rocks. Observations accumulated by the author 

 •Hiring the last twenty years on occurrences of this diorite scattered over many 

 thousand square miles now seem to justify attributing the formation of this 

 rock to metamorphism. 



The rock occurs in bodies of various shapes, in which an ellipsoidal element 

 is usually seen. In places it forms sheets with rounded or lenticular edges 

 and rarely has the aspect of a lenticular dike. The most prominent relations 



