north of the western end of the railroad station (and the station is so close beyond the bridge that a small corner of the platform can be seen in the picture, beyond the right-hand abutment) an artificial rock exposure begins and extends nearly fifty yards westward, with unmistakable dips of forty degrees, south about fifty-three degrees west.

7. In the space, however, between the danger-post and the strongly marked dips of the eastern half of the eastern view, the structure is not so uniform, and is not so clearly shown by the photograph, nor indeed so easily made out on the ground. Ten yards along the cutting east of the danger-post and opposite the eastern end of a small stable on the top of the south side of the cut, and in the picture a little to the left or directly beneath the right-hand telegraph pole, in the rather smoothly rounded projecting rock mass, there is a small rock saddle, or anticlinal, that can be seen on the ground with some care, and can even be perceived in the photograph, especially where the layers about the midheight of the cut begin to bend over from the westerly dip. Six yards further east, on the western side of the first small depression or slight gully, and five yards west of the first strongly marked southwesterly dip surface, and in the picture almost directly below the telegraph pole, there is a small rock basin or synclinal, somewhat difficultly discerned in the photograph, yet still decidedly perceptible there with a little patience, particularly with the help of a strong magnifying glass, and quite visible on the ground. The partly obscure portion of the section, then, is at most a dozen or fifteen yards of the length of the cutting; and at right angles with the strike not more than eight or ten yards; and, as the photograph shows, it is apparently not the part represented by Prof. Lewis's sketch. It appears unfortunately impossible to make the dips of that portion extremely obvious in a photograph; but on the ground they can be seen with a little care, and have been distinctly recognized, not only by myself, but by Mr. Harden, and, in December, 1888, by Dr. Amos P. Brown and Mr. J. S. Elverson. The place is now so precisely pointed out that it can readily be identified by any one visiting the spot, and he can see for himself the accuracy of the description of the structure.

8. It is evident, then, that the rocks of the cutting are by no means fault rock, but merely steep-dipping and somewhat folded dark gray and dark red beds of the Gwynedd Shales, cut across at a sharp angle with the strike and much fractured with ordinary cleavage planes of many directions, and requiring for a perception of the structure to be observed at an angle of not more than forty-five degrees with the railroad instead of at right angles. The chief geological interest and value of the rock exposure, therefore, is not in its displaying a fault of otherwise incredible dimensions, with the unheard-of width of a hundred feet or more, and with the inconceivable heave of four or five miles for a nearly vertical trap dike; but in its showing how it may sometimes be a little difficult to distinguish the true bedding and dip among many confusing cleavage planes. The great fault, coming westward from the southern