500 PROCEEDINGS OF THE NEW YORK MEETING 



South Greenwich, south of Providence, Rhode Island, and a quartz-porphyry and 

 granite containing hlue quartz were especially descrihed. South of the Boston area 

 these granites do not alter the Cambrian schists and do not absorb any material 

 from them. Several other bands extending across Worcester county were con- 

 trasted with the Quincy band in the following particulars : They are often coarsely 

 porphyritic, while the Quincy granites are not. They are microcline granites. The 

 Quincy granites are orthoclase granites. They contain biotite or biotite and mus- 

 covite instead of biotite and hornblende or glaucophane. 



These granite batholites are also contrasted with the Quincy rock in having a 

 broad peripheral layer which has all the peculiarities of pegmatite in some cases, 

 and grades into black albitic granites or even quartz-diorites. 



These differences are largely due to the fact that these rocks have fused much 

 of the surrounding schist into their composition, and this was proved by finding 

 characteristic inclusions of the schist in great numbers and of every size in the 

 granite, and also by tracing these inclusions into smaller and smaller filaments 

 until they faded from sight, and finding with the microscope far beyond this point 

 in the ft-esh granite clear traces of the schists. When the schist contains pyrite, 

 garnet, fibrolite, cordierite, or graphite, the granite becomes more ferruginous and 

 garnetiferous. The amber coarse fibrolite of the schist appears dissolved and re- 

 crystallized as a white, silky bucholzite or fazer-kiesel in the granite, and the 

 graphite scales are inclosed in all the constituents of the grajiite over many square 

 miles. 



Over the whole surface of the great Hubbardston batholite of perfect, coarse por- 

 phyritic granite 32 miles long and 6 miles wide it was possible to map the areas once 

 occupied by the different schists, which formerly mantled over the granite mass by 

 means of the indestructible constituents of the former schists ; by the portions which 

 had melted into the mass of the granite ; by the filaments still remaining unabsorbed, 

 and by the diff'erent aspect of the granite, dependent largely on the gi'eat increment 

 of iron. Using especially the first two criteria, this double mapping of the region 

 will be carried out in the sheets being prepared for the United States Geological 

 Survey. 



The region extending for several miles south from mount Wachusett and that 

 north and south of Brookfield in the Hubbardston batholite furnish abundant 

 exposures for the study of the phenomena here described. 



The paper was discussed by Whitman Cross, M. E. Wadsworth, J. F. 

 Kemp, and the author. Two papers by Kemp followed : 



METAMORPHOSED BASIC DIKES IN THE MANHATTAN SCHISTS 

 BY J. F. KEMP 



Remarks were made b}^ M. E. Wadsworth. 



GRANITES OF SOUTHERN RHODE ISLAND AND CONNECTICUT, WITH OBSERVA- 

 TIONS ON ATLANTIC COAST GRANITES IN GENERAL 



BY J. F. KEMP 



Remarks were made by J. E. Wolff. The paper is printed as pages 

 361-382 of this volume. 



