IM PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORl . 
the Maiiliiis, althmigh in his footnote Mather was careful to 
state that nowhere were the rocks of the two syst(ans actually in 
contact. It was, however, a justifiable assumption. That it 
could not be altogether justified is clearly seen from an examina- 
tion of a paper })y Davis,' from which I Cjuote Ix'low. For the 
reason that no newer information about the structure of the 
mountain has come to my notice, these conchisions have been 
assumed by me. 
"The observations thus detailed [the eight places where a 
contact of the Manlius with the Hudson beds can most nearly 
be seen] may be summarized as follows: A, C, and G are non- 
committal; if necessary they could agree with either conclusion. 
B and H, if seen alone, would be taken as decisive of conformity. 
D, E and F imply unconformity, but with nothing of the dis- 
tinctness shown in Mather's section. . . . 
"... There is therefore no necessity of supposing uncon- 
formity at Becraft's Mountain simply because the limestones 
there do not belong immediately after the shales in the 
geological series. Moreover, the generally flat position of the 
limestones and tilted position of the shales east of the Hudson 
does not decide the question, for the shales are twice seen almost 
flat under the limestones of the outlier, and on the southeastern 
side the limestones are strongly tilted. . . . This indefiniteness 
of indirect evidence is the more unsatisfactory from the incom- 
pleteness of the contact outcrops; and as it is very possible for 
an appearance of nonconformity to arise in a 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." 
Rondout, N. Y. — At Rondout there is apparently a clearly 
defined case of an unconformity between the Ordovician and 
Silurian (or, as has been recently suggested by Schuchert, Lower 
Devonian) strata. This has been described and figured by 
Mather, Davis, and Van Ingen and Clark. From these reports 
^Davis, W. M. Becraft's Mountain. Amer. Journ. Sci., ser. 3, vol. 
26, p. 381-389, 1883. 
