WARREN. — ALK-A.LI-GRAXITES AXD PORPHYRIES. 205 



of the granite from various quarries, quantitative estimates of the 

 mineral composition as well as many interesting and valuable state- 

 ments regarding the grain, joint structures, and other features relating 

 to the economic aspects of the granite and quarries. 



A recent paper by G. F. Loughlin ^ discusses the geology of the area 

 particularly with reference to the prol)a1)le relations of the intrusive 

 rocks to the associated sedimentary formations. 



The pegmatites occurring in two of the quarries on North Common 

 Hill, Quincy, have been described together with their minerals by 

 Charles Palache and the writer.^ 



During the earlier part of the writer's work on these rocks he had 

 the assistance of Dr. J. D. Trueman who was at that time pursuing 

 studies leading to the degree of Master of Science at the Massachu- 

 setts Institute of Technology, and whose recent lamentable death by 

 drowning while working for the Canadian Geological Survey has 

 deprived geology of one of its most promising and enthusiastic 

 workers. The preliminary results obtained by Dr. Trueman were 

 embodied in his Master's thesis and the writer wishes to acknowledge 

 his indebtedness to Dr. Trueman for much carefid and discerning 

 field and laboratory work. 



Almost the entire field has been gone over with great care by the 

 writer in person, and in this task he has been greatly helped by the 

 exceedingly full descriptions contained in Professor Crosby's memoir, 

 and has had the further advantage of the latter's company on se^■eral 

 field excursions and of his keen interest in the work throughout. 



The author wishes here to express his thanks to the Metropolitan 

 Park Commission for permission to collect specimens within the Blue 

 Hill Reservation. 



Summary of the geology of the area. — Those wishing to inform 

 themselves regarding the general geologic features of the area are 

 referred to the paper by G. F. Loughlin, previously mentioned, or in 

 case more detailed information is desired, the memoir of Professor 

 Crosby should be consulted. It will be sufficient here to give only a 

 very brief summary of the geology. 



The alkaline rock series, as it may be called, occupies a roughly 

 elliptical area having a nearly east-west major axis of about 9 

 miles (15 km.) in length, and a minor axis of from two to three miles 

 (3 to 5 km.). Its eastern end lies near the Weymouth-Fore river. 



8 American Journal of Science, 32, (July, 1911). 



9 These Proceedings, 47, No. 4 (July, 1911). 



