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 several surveys of the mountain, however, prove it to be 212 feet higher than Sugar Run Gap, and, to reduce it to a level with the surface of the ground at the latter point, which is 120 feet above the grade of the adopted line, it would require a tunnel 1¼ miles in length, to be constructed under very disadvantageous local circumstances. Cedar Swamp Gap, still farther south, is 53 feet lower than Bob's Creek Gap, but it falls off on each side so gradually that it could not be reduced conveniently more than 40 feet. Neither of these points, therefore, which are the only passes worthy of notice south of the Portage Railroad that lie within the region over which a direct line to Pittsburg must necessarily traverse, afford depressions that will compare favorably with those farther north; nor does the ground leading to them, east or west of the mountains, offer equal facilities to obtain a line of uniform ascent to the summit. The distance from the Conemaugh is too short to overcome the elevation with the gradient used on the western division, and, from the Juniata, the greater height to be ascended would continue the line so long upon the mountain steeps that it would be exceedingly expensive to procure a roadbed with a gradient even higher than 80 feet per mile.