W. M. Davis—Nonconformity at Rondout. 389 
outlier, and on the southeastern side the limestones are strongly 
tilted. The suggestion above that the shales and slates are of 
different ages requires much further observation for its proof. 
This indefiniteness of indirect evidence is the more unsatisfac- 
tory from the incompleteness of the contact outcrops; an i 
18 very possible for an appearance of nonconformity to arise in 
@ series that is all folded at the same time, on account of the 
unequal folding of adjoining strata of different resistances, 
nothing but direct and clear exposure of an uneven and surely 
unconformable contact will suffice finally to settle this point in 
the structure of Becraft’s Mountain. 
Cambridge, April 23, 1883. 
Art. XLV.— The Nonconformity at Rondout, N. Y.; by 
: W. M. Davis. 
Description of the formations occurring here—Upper Silurian unconformable on. 
oak Lower—Altitude of the rocks and local topography—Glacial and surface. 
Seology. 
THE reference made in the preceding article on Becraft’s. 
Mountain to the clear evidence of the unconformable relation. 
of the Upper and Lower Silurian rocks at Rondout on the 
Hudson su gests the publication of a more detailed illustra- 
and sometimes shaly and much contorted, g 
of the stream at Eddyville. They occupy all the area east of 
* Poughkeepsie Soc. Nat. Sci. Proc., ii, 1879, 44-48. : 
+ This Journal, xviii, 1879, 293-295.  Dale’s figures belong near section II om 
our D. 
_ $1, and Bull, Mus. Comp. Zool., Geol. Series, i, 1883, 311-329. 
