Authority.
It will be perceived that the lowest point in the mountain, except at Emigh's, is Maple Gap, from which issues Bell's Run (a branch of the Little Juniata), on the east, and Sandy Run of Clearfield, on the west. This point is 61 feet below Sugar Run Gap and could be further reduced 150 feet by a tunnel 700 yards in length. If the ground had been favorable beyond the summit, this route would probably have offered the greatest advantages to cross the mountain, but it opens westwardly upon the deep valley of Clearfield, a descent into which would involve the necessity of a resort to as steep a gradient on the west side of the mountain as that required on the east; and the elevation thus lost would have to be regained by following up the valley to Laurel Swamp or Munster summits, in the ridge that separates Clearfield from the Conemaugh, which is here the true backbone of the country.
Any attempt to carry a line along the west slope of the mountain, to avoid the descent to Clearfield, would, from the rugged character of the ground, prove impracticable, without a vast increase in its cost, length and curvature. No other point offers equal advantages to cross the mountain until we reach Sugar Run Gap, which is 41 feet below the Portage Railroad summit, and may be reduced 120 feet more by a tunnel 2,000 feet in length. Emigh's Gap, which is still lower than Maple Gap, could not, on account of its gradual slope, be reduced by a tunnel of moderate cost, and it is also too far north for a direct route to Pittsburg. South of the Portage the Alleghenies become the watershed of the Union, dividing the streams that flow into the gulf from those that empty into the Atlantic. They here assume a more elevated character than while separating only the tributaries of the Susquehanna, affording no opportunity to pass them by a line adapted to locomotive power—unless by a tunnel of immense extent—until we reach Bob's Creek Gap. The accompanying profile, which exhibits the crest line of the mountain (for 44 miles) will give a more definite idea of the relative height of these summits.
The mountain on each side of Bob's Creek Gap rises to a considerable height, making it appear, to a casual observer, a very deep depression; and, from this circumstance, it has generally been considered by the residents of the adjoining country to be the lowest pass in the Alleghenies, and, as it falls off rapidly on either side, it has also been supposed that it could be farther reduced by a tunnel of moderate extent. The
