The Railway Library, 1909. VariousЧитать онлайн книгу.
most important and difficult district upon the whole route to Pittsburg.
These parties did not take the field until the close of July, but they prosecuted their examinations with so much energy and success that we were enabled to determine the general line of the eastern division in season to place the most difficult points upon it under contract in November of last year.
While these arrangements were in progress, the parties previously in the field were actively engaged in examining the country between Harrisburg and Lewistown.
At the instance of a number of gentlemen from Perry county, a line was tried up Little Juniata creek, leaving the Susquehanna at Petersburg, thence near Bloomfield and along Sherman's valley to Concord gap, where it passed the Tuscarora mountain, thence it followed Tuscarora valley to Shade creek, and down that stream to Augwick creek, along the valley of which it was carried to Drake's ferry on the Juniata. The advantage promised for this route was a considerable saving of distance. The result, however, demonstrated that not only would we have had to encounter gradients running up as high as sixty feet per mile, but the length of the line would be increased four miles by its adoption. It was consequently abandoned.
After a careful examination of the country bordering on the Susquehanna and Juniata rivers, a line has been located as far up as Huntingdon, which is believed to be the best that can be obtained.
If the valleys of these streams had not been preoccupied by other improvements, a route would have been selected differing somewhat in its details from that adopted. Even for the short distance that we are brought into close proximity with them, the cost of the grading of the Road has been greatly enhanced by the confined ground we have been forced upon.
The located line commences at the Harrisburg and Lancaster Railroad depot; thence, passing through Harrisburg, it follows the sloping ground between the canal and the capitol ridge four miles, when it crosses the canal and, touching the point of Blue mountain, recrosses and passes to the west side of the Susquehanna river by a bridge 3,660 feet in length, and 44 feet above low water at grade line, which enables us to place the road on the top of the bridge. Thence we pursue this bank of the river through the villages of Duncannon and Petersburg to the Juniata, along the southern side of which it is continued through Newport and Perrysville to a point a short distance above Lewistown. Here the line crosses to the north side of the river, and within a short distance recrosses, to save nearly a mile of road, and one hundred and eighty degrees of curvature, together with some difficult ground along the bluff shores on the south side of the stream.
After regaining the southern side we follow the river slopes, over favorable ground, to Mr. Harvey's, about seven miles above Waynesburg, where the line again crosses to the north side, and passing back of Newton Hamilton, cuts through the neck of land in the great bend of that stream, 40 feet in depth at the summit and 3,100 feet in length at grade. Descending along the eastern slope of the river, we once more cross it at Shaeffer's aqueduct, and continue upon its southwestern bank through Jack's narrows, without meeting any serious difficulties, and finally pass to its north side, along which it is continued through Huntingdon to the Little Juniata, above Petersburg. Above Huntingdon, a preliminary location has been carried up the Little Juniata to Logan's narrows, at which point this stream divides Bald Eagle and Brush mountains in its passage from Tuckahoe valley.
Along the Little Juniata, from Dorsey's forge to the Narrows, the line encounters much difficult ground, owing to the circuitous character of the stream, and the high hills and mountains which bound its course. To obtain a route with easy curves we are forced, within this distance, to tunnel the point of Tussey's mountain, and to cross the river twelve times. To follow the line recommended by Mr. Schlatter through this region curves of 400 feet radius would have had to be resorted to, which I deem wholly inadmissible upon a road of the importance of that you have in view.
At Logan's Narrows we reach the valley that skirts the whole eastern base of the Allegheny mountains. Here it becomes necessary to determine the plan to be adopted to overcome the great barrier that separates us from the West. If it is to be surmounted by a road, with the gradients of the western division, the ascent must commence at this point, and gradually wind its way to the summit, by an almost continuous gradient, along the declivities of the mountains for nearly thirty-two miles, crossing the several streams that issue from it, by high bridges, and cutting through or tunneling their dividing summits.
Mr. Schlatter, in his Report to the Canal Commissioners, estimates the cost of grading the road, on this ascent, at $1,496,146, which I consider too low for a line with the gradient he adopted, but with the increased maximum grade found necessary on the western division, and a somewhat lengthened line, it would probably prove sufficient.
Upon my first reconnoissance of this portion of the country it occurred to me that its peculiar topographical features were lost sight of in the adoption of this plan of ascent, which seemed to look to the single object of obtaining a line with a particular gradient, without regard to the magnitude of the obstacles to be overcome to procure it; while, by pursuing a course from the Narrows, nearly in a direct line to Sugar Run gap (which we shall hereafter show is the best point to cross the mountain), the line would pass through a beautiful valley over comparatively favorable ground, gradually gaining elevation through its whole course, without exceeding the maximum inclination required on the line below, until it reaches the summit of the valley at Robinson's, a distance of fifteen miles. At this point we attain an elevation of 1,174 feet above tide, leaving but 980 feet to be overcome to reach the height found most suitable for passing the mountain, which is attained by a continuous gradient of 80 feet per mile, encountering no very formidable difficulties.
A resort to a gradient of 80 or more feet per mile is by no means an unusual expedient on leading railroads.
Upon the Western Railroad, in Massachusetts, their maximum gradient is 83½ feet per mile. On the Baltimore & Ohio Railroad they now have, between the waters of the Patapsco and Potomac, on each side of Parr's ridge, gradients of 82 feet per mile, and from the greater elevation of the Allegheny mountains at the place they must cross, it is to be presumed that their gradients at that point will still be increased to a higher rate.
Many other instances might be cited, some running up to 120 feet per mile, but it seems unnecessary to extend the list. Theoretically, the power necessary to overcome a given height is the same at all inclinations of the plane of ascent, but in practice, it is to some extent dependent upon the kind of power to be applied.
In the case under consideration, the locomotive steam engine will be the medium used, where the power is carried with the train, and forms part of the load to be moved, consequently, the cost of power on a plane ascending 80 feet per mile is greater than upon one of a more moderate inclination of equal height, by the difference between the gravity of the engines required to carry the same load on both planes.
As a general principle this would be true when the lengths of the roads to overcome the same height are equal, and it is necessary to carry the locomotives, required for the high gradient, over the same distance that they must run upon the low gradient.
But in one of these cases the maximum gradient due to the line below Logan's Narrows is carried to within 12¼ miles of the summit of the mountain—requiring extra power for that distance only—and in the other it ends 32 miles from it.
To explain more fully the relative value of the maximum gradients used on the different divisions of our Road, I have prepared the following table:
Table headings:
Col A: Division of Road.
Col B: Maximum Gradient, ascending westwardly, per mile.
Col C: Maximum Gradient, ascending eastwardly, per mile.
Col D: Gross load of a 20 ton freight locomotive,
exclusive of engine, and a tender of 10 tons. Friction
8½ lbs. per T. Adhesion ½.
Col E: Load of merchandise for a 20 ton freight engine,
the cars being estimated at 4/10ths of their
weight and load.
Col