80 TRANSACTIONS OF THE [FEB. 18, 
STATED MEETING. 
February 18th, 1895. 
The Academy met and was called to order by the Secretary. 
In the absence of the President it was moved and carried that 
Prof. J. J. Stevenson take the chair. Twenty-four persons were 
present. The following paper was read by title and referred to 
the Publication Committee : 
H: G. Dyar;:* fhe Bacteria in the Air of New York.” 
The Section of Geology and Mineralogy at once organized 
and the minutes of the previous meeting were read and ap- 
proved. The first paper was the following: 
ON A GRANITE-DIORITE NEAR HARRISON, WEST- 
CHESTER COUNTY, N. Y. 
By Hetnricu RIEs. 
The greater portion of Westchester county is formed of a 
series of metamorphic rocks, which, according to Merrill,* com- 
prise the following members : ‘ 
1. A basal red gneiss, called the Yonkers gneiss. 
2. A grey gneiss, called the Fordham gneiss. 
3. Quartzite. 
4. The Inwood limestone or dolomite. 
5. Mica-schists or Manhattan schists. 
These rocks extend across the county from north to south, 
in more or less parallel bands, and show a high dip. In the 
eastern portion of Westchester county the rock is a mica-schist 
which becomes highly quartzose along the shore of Long Island 
Sound. 
The only igneous rocks thus far described from Westchester 
county are the well-known Cortlandt series} of diorites and gab- 
bros near Peekskill, N. Y., which were studied and described in 
detail by the late Prof. G. H. Williams, and also by Prof. J. D. 
Dana.{ In addition Dr. Merrill calls attention to many locali- 
ties of hornblendic and augitic strata, rarely more than a few 
feet in thickness, which are probably metamorphosed eruptive 
* Amer. Jour. Sci., iii., XXXIX., 383. 
tIbid. iii., XXXV., 488; XX XI., p. 26; XX XITI., p. 135-191. 
TEAS le Seg Lil. pNGROU., elOss 
