90 TRANSACTIONS OF THE [DEC. 16, 
cations occurs, interbedded between normally horizontal layers, 
which constitute a great thickness both above and below. The 
phenomena is diagrammatically figured by Vanuxem on page 
53. 
There is a series of these folds, more or less covered by debris 
at the surface outcrop, three or four of the most striking of 
which are shown in the photograph (plate III, figure A), es- 
pecially the one a little to the right of the centre of the view. 
The trough of the plications bears N. 50° E. The “rim,” if we 
may so term the exterior of the troughs, which most resists 
weathering on the exposed surface, is of one of the blue-black 
compact layers, two or three inches thick, so frequent in zone 
D 15, of which it forms a part. That the distortion has not been 
accompanied by metamorphism is demonstrated by the fact that 
the more shaly layers, both within and without this denser “rim,” 
which coincide with its curve, preserve their fossils (Plectam- 
bonites and Orthids) intact. Vanuxem considers that the con- 
tortion was due to a crystallization of the “rim ” layer, necessi- 
tating expansion; while Prof. W. O. Cr osby has suggested to 
the writer that the cause may have been the yielding of this 
layer under the tremendous weight of strata above. Either 
theory, however, would imply metamorphism, which does not 
exist. JI am inclined to think that the contortion took place, 
from some cause, very shortly after the period of deposition. 
A photograph of the Great Falls, where the phenomenon oc- 
curs, is given by N. H. Darton, Plate X, 47th Annual Report, 
N. Y. State Museum. 
Various peculiar contortions of the strata are to be noted. 
The first of these is on the eastern face of the narrow passage 
known as “ Rocky Heart,” shown in plate III, figure B. The 
upper layers are nearly horizontal, while those below show over- 
lap structure, due to the subsequent settling and resedimenta- 
tion upon the original shore. The layers alternately thicken as 
shown, the stratification following the contact surface with the 
older sea bottom. 
Several other such cases may be noted ; and another probably 
similar instance from the upper end of the gorge, in the layers 
of section D 22, is shown near the center of plate V, figure A. 
Near to the latter one of the exits of the underground streams, 
flowing along the solution crevices of D. 23, pours its rill into 
the creek from a considerable height. 
Near the same locality, also in D 22, there occurs a striking 
example of what is probably an ancient channel filling, shown in 
Plate IV, figure B. The edge of the channel forms with the adja- 
cent horizontal layers in which it rests an angle of 8 to 15°. The 
