372 J. D. Dana—Geological Relations of the. 
torsion. The limestone areas are commonly the positions of 
upward or downward folds or flexures, with usually the axis in 
each case inclined in the direction of the fold and the axial 
plane also inclined to one side or the other; and in the making 
of them, contortions should have been often produced. The 
small serpentine area at Rye, No. 6, is a striking illustration ; 
and the north end of area 28 is another. The varying strikes 
between areas 24 and 25 show the effects of torsion and the 
interference of the near extremities of two curving folds. 
2. Relation to the Green Mountain System. 
With reference to the relation of the rocks of the county to 
ij 
of the Green Mountain elevation. The axis passes along the 
interlocking borders of Connecticut and New York, and 
least degrees of metamorphism are found in the limestone and 
associated schists of the vicinity of Peekskill, in the northwest 
corner, while along the central and eastern portions of the 
county, and in the western, also, south of Croton, the crystalli- 
zation is commonly very coarse. The limestone of the Ver- 
planck, Cruger’s and Croton areas (Nos. 28, 27, 18), are of inter- 
mediate texture. 
(3.) The limestones have the same kinds of associated rocks, 
that is, of mica schists and gneisses, as in the eastern and more 
metamorphic portion of the region in Connecticut—a fact 
deserving mention though not of great weight. 
; e limestones have a like paucity in disseminated min- 
erals and similar occurring species with those of Connecticut ; 
mica (muscovite) and tremolite being the common kinds, white 
pyroxene of occasional appearance, and graphite sometimes 
present. 
(5.) The ordinary normal trend of the rocks, N. 20° E. to N. 
30° E., is very nearly the average trend of the beds of limestone 
and associated rocks in the Green Mountain system. 
Through the Southern and Middle sections of Westchester 
County this trend or strike is almost uniform, except where 
great contortions occur; and on the east, this strike is continued 
northward into Connecticut. In the Northern section, on the 
contrary, the exceptions, excluding its eastern and northwestern 
portions, are almost universal; and the question is a serio 
one whether another system is not here represented. But, in 
opposition to this inference, we observe that the limestones and 
