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MUSEUM OF COMPAKATIVE ZOOLOGY. 



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WethcrBficld, give clear explanation of the two causes that have produced 

 the crcsccntic outlines so characteristic of the trap. The first (1) is 

 shown to be a flat fold, a faint canoe-synclinal outcropping to the north 

 and west, by the close parallelism of the sandstone ledges around its 

 front ; their strike changes so as to run parallel to the trap bluff, and 

 they dip towards and under it on three sides. The trap shows a steep 

 face on the convex, and a long gentle slope on the concave side of its 

 crescent. It is undoubtedly a thin overflow sheet; for although no 

 contacts were scon, nonnul red sandstone was found three feet below 

 the trap, and red shaly sandstone fifteen feet above it, on a cross-road a 

 quarter of a mile southwest of Beckley Station ; and the trap is compact 

 at the bottom, and very loose and amygdaloidal on top. Evidently, 

 then, the sandstones and the trap have been here slightly folded to- 

 getlier, and erosion has revealed their canoe-form precisely as it has 

 brought out the greater canoes of Medina Sandstone in Pennsylvania. 

 The eastern side of the canoe is not visible except at its northern end, 

 or bow as it may be called, because the fold is canted over on the east. 

 The fold as a whole has a gentle eastward dip. 



The second curve (2) is made of trap much like that of the first, and 

 it is very probably the same trap sheet brought to the surface again by 

 a north and south fault with upthrow of forty or fifty feet on the east; 

 its curve docs not seem to depend on a fold, but simply on the cross 

 valley of the Mattabesio ; for a stream cutting through a monoclinah 

 ridge always produces such a retreat in the outcrop line of its deter- 

 mining hard stratum. The second and third crescents are therefore to 

 be regarded as parts of a single fold, cut into the imitation of a double 

 fold by the stream between them. 



It becomes, therefore, an important matter to determine which of the 

 crescentio ridges shown in Percival's and other maps are due to folding 

 of the trap sheets, and which to erosion withoxit folding; E. I. and 

 E. 11. are undoubtedly folds; so is the great curve of E. IV. that runs 

 up into Massachusetts. New Jersey shows several others. But the 



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peculiar forms of E. IV. 1, 2, 3, are chiefly, if not entirely, duo to erosion, 

 as is shown under the next heading. 



Percival gives a close description of the facts about Beckley (358), 

 but makes no statement of their cause, 



E. Meriden, Conn. (figs. 40 ~ 43). — Two days' walking about the 

 Hanging Hills and Lamentation Mountain failed to discover any con- 

 tacts, very probably on account of keeping mostly to the roads so as 

 to cover more ground, for the work here was chiefly stratigraphical. 



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