34 THE GEOLOGIST'S TRAVELING HA^D-BOOK. 



11-12. UPPER DEVONIAN. 



11 a. Portage. This group represents an extensive development of shales 

 and flagstones, and finally some thick-bedded sandstone towards its upper part. 

 It is extremely variable in character at different and distant points. In New York 

 the Portage rises sometimes in a gentle slope, and at other times abruptly from 

 the softer shales below. Between the deep north and south valleys, in which the 

 railroads run, the enduring sandstones of the upper part extend far northward, 

 presenting, on the north side, a gentle slope, while on the east and west sides of 

 the same hills, the slope is abrupt, the valleys being bounded by steep hills. The 

 change in the external appearance of the country indicates the commencement of 

 thesi Portage rocks, although they are not seen. Throughout the Hamilton shales, 

 the valleys present gently sloping sides, and the country rarely rises far above the 

 valley bottom. But on approaching the northern margin of the Portage group, the 

 railway traveler sees a gradually increasing elevation of the hills on either side, and 

 an abruptness hi their slope, and in a short time finds himself in a deep valley 

 bounded on either side by hills rising 400 or 500 feet, and in some instances, even 

 800 feet above the bed of the stream. These elevations often extend several miles 

 unbroken, except by the deep ravines which indent their sides. The higher sand- 

 stones of the group, and in many instances the intermediate ones, produce falls in 

 the streams which pass over them, and some of the most beautiful cascades in the 

 State of New York, and many of the highest perpendicular falls of water, are pro- 

 duced by the rocks of this group, and in none others do we meet with more grand 

 and striking scenery. J. Hall's Report. 



The pedestrian often finds his course impeded by a gorge of several hundred 

 feet in depth, such as Watkins Glen and Havana Glen. The Portage upper, middle 

 and lower falls are 66, 110 and 96 feet, and between the middle and lower the 

 rocks rise in perpendicular cliffs 351 feet in height. See note No. 110, New York, 

 as to Portage on Erie Railroad. Taghanic, Hector, and Lodi falls are also in the 

 Portage. These points afford some of the grandest views of scenery, and 

 admirable facilities for geological investigations. The lower division of the 

 Portage is the 1. Ohasagua shales, a green shale, with thin flagstones, and sandy 

 shale. 2. The middle portion is the Gardeau shale and flagstones, a great 

 development of green and black slaty and sandy shales, with thin layers of 

 sandstone, from which are quarried beautiful and durable flagstones. The 

 rocks of this part of the group form high, almost perpendicular, banks on the 

 Genesee. In a westerly direction the sandstones disappear, and the shales increase. 

 8. The upper part of the Portage consists of the Portage sandstones, thick 

 bedded sandstones, with little shale, while below, the sandy layers become thinner, 

 and shale beds more frequent ; still it must be acknowledged that there is no abrupt 

 change from the beginning of the Portage to the top of the Chemung. In the 

 Portage, the sandstones and shales are less separated than above, and the sandy 

 strata are finer grained, and contain more lime than in the Chemung. Towards the 

 southern extremity of Cayuga and Seneca Lakes, the Portage rocks form cliffs of 

 considerable height, which present alternating hard and soft layers, and the 

 numerous vertical joints present the appearance of solid walls of masonry, in 

 distinct and regular courses. The vertical joints are well seen in Havana Glen. 

 Isolated masses, like huge columns, are often seen, standing out in bold relief 

 from the line of the cliff, being the remains of previously exposed surfaces, which 



