140 



SCIENCE. 



[N. S. Vol. IX. No. 213. 



Ararat to that of Shasta, and others said 

 the same of Shishaldio. 



The Society then adjourned for lunch. 



PETROGRAPHIC SECTION. 



On reassembling for the afternoon session 

 the Society divided into two sections, in 

 order to finish the program. The petro- 

 graphic section listened to the following 

 papers : 

 Differences in Batliolitlc Granites According to 



Deiith of Erosion. B. K. Emerson, Am- 

 herst, Mass. 



The speaker reviewed the distribution of 

 granitic rocks in Massachusetts, illustrating 

 his remarks with a sketch map of it and of 

 the neighboring States to the south. He 

 commented on the tonalite near Northamp- 

 ton, the Cape Ann area, the Quincy area 

 and the extension of quartz porphyries and 

 felsites to the southwest of the last. He 

 outlined another belt of igneous rocks that 

 passes near Worcester. He then developed 

 the idea regarding the tonalite that it had 

 fused its way upward, involving in itself 

 the overlying schists to such a degree that 

 zones can be traced around the granite 

 proper that mark the various stages of ab- 

 sorption or metamorphism of the schists. 

 From the granite outward there is a fibro- 

 litic zone, then a chiastolitic, next an an- 

 dalusitic and lastly the schists. Given one 

 of these zones, such as the chiastolitic at 

 Lancaster, the presence of the granite may 

 be confidently predicted in depth, although 

 not actually visible. The demarcation of 

 the zones is sharp enough to admit of 

 mapping. 



The next two papers followed before dis- 

 cussion. 

 Metamorphosed Basic Dikes hi the Manhattan 



Schists, New Yorh City. J. F. Kemp, ISTew 



York City. 



Hornblende schists in narrow belts have 

 long been known in the j^revailing mica- 

 schists of Manhattan Island. This paper 



describes one special occurrence on Morn- 

 ingside Park, between 118th and 119th 

 Streets, near the Columbia University Cam- 

 pus. A small detailed map was shown, 

 together with analyses and petrographic 

 details of the amphibolite and of the mica- 

 schists. The speaker stated that the am- 

 phibolite must be referred to an igneous in- 

 trusion or to limey bands in the schists. 

 The most reasonable interpretation seemed 

 to him to be the igneous. The rocks were 

 illustrated by projecting thin sections with 

 a polarizing microscopic lantern. 



The Granites on the North Shore of Long 

 Island Sound, with some Observations on the 

 Granites of the Atlantic Coast in General. 

 J. F. Kemp, New York City. 

 The general character of the crystalline 

 rocks along the sound from New Haven to 

 Narragansett Bay was outlined, and it was 

 shown that they are chiefly granitic gneisses, 

 with pronounced foliation, but with some 

 augen-gneiss and considerable basic horn- 

 bleudic and biotitic schist. The granites 

 at Niantic and Westerly, E. I., and at 

 New London, Millstone Point, Stony Creek 

 and some minor localities in Connecticut 

 were discussed. They were shown to be 

 biotite-granites of several varieties. Al- 

 though they have nearly or quite the same 

 mineralogy as the prevailing gneiss of the 

 region, their intrusive character was shown 

 by their relations to the wall- rocks and by 

 their peculiar inclusions of the basic horn- 

 blendic and biotitic schists. The supposed 

 Carboniferous age of the Connecticut gran- 

 ite, as advanced by Pirsson,was mentioned as 

 perhaps indicating a fairly late age for those 

 in the gneissic areas. Slides of the rocks dis- 

 cussed were afterwards thrown on the screen 

 with the polarizing microscope. The remark- 

 able development of pegmatites that every- 

 where characterize the region was also dis- 

 cussed, both as regards mineralogy and 

 geological relations. They vary from coarse 



