220 PEOCEEDINGS OF THE ACADEMY OF [1896. 



The rock of the Conshohocken dyke is medium-grained, compact, 

 of a gray color on the fresh surface, a rusty green on the weathered 

 surface. In thin sections it shows itself a typical diabase, with 

 plagioclase, pyroxene, ilmenite and apatite, as primary constituents, 

 and chlorite, serpentine, scanty biotite and calcite, as secondary 

 constituents. The structure is characteristically ophitic: slender 

 idiomorphic lath-shaped feldspars form a net work, while allotrio- 

 morphic pyroxene fills the angular spaces. The feldspar is twinned 

 according to the albite law, and its optical properties indicate that 

 it belongs to the labradorite-bytownite end of the series. The py- 

 roxene is a colorless nonpleochroic monoclinic variety. The cleav- 

 ages and low extinction angle point to diallage as the species. Apa- 

 tite is the oldest constituent. Ilmenite shows slight alteration to 

 leucoxene. The rock is very like the Pine Rock diabase described 

 by Dana in Amer. Jour. Sci., Vol. 42, 1891, page 82. 



April 14. 

 The President, Samuel G. Dixon, M. D., in the Chair. 

 Twenty-seven persons present. 



April 21. 



The President, Samuel G. Dixon, M. D., in the Chair 



Thirty-six persons present. 



A paper entitled " A Revision of the Polar Hares of America," 

 by Samuel N. Rhoads, was presented for publication. 



April 28. 

 The President, Samuel G. Dixon, M. D., in the Chair. 

 Thirty-three persons present. 



A paper entitled " A Remarkable Central American Melanian," 

 by H. A. Pilsbry, was presented for publication. 



The death of William Hunt, M. D., a member, April 19, 1896, 

 was announced. 



Dr. Persifor Frazer was appointed to represent the Academy 

 at the Seventh Session of the International Congress of Geologists 

 to be held in St. Petersburg in 1897. 



An invitation to participate in the Mining and Geological 

 Millennial Congress, to be held at Budapest, September 25th and 



