Читать книгу The Railway Library, 1909 - Various - Страница 5

Table of Contents

June 12, 1848.

By J. Edgar Thomson.

Chief Engineer.

Engineer Department, Pennsylvania R. R. Co.

Philadelphia, June 12, 1848.

To the President and Directors of the

Pennsylvania Railroad Company:

Gentlemen—I have the honor to communicate to you the following Report of the operations of this Department since it was committed to my charge, now something more than a year.

Under the organization of the Engineer Department, as adopted previous to my acceptance of the office you have conferred upon me, the Road was to be divided into three divisions, Eastern, Western and Middle: Edward Miller, Esq., as associate engineer, was assigned to the Western, and W. B. Foster, Jr., to the Eastern division. These gentlemen had entered upon the survey of their respective lines, previous to my arrival, under instructions from the president, each with two full corps of assistants. The middle, or mountain division, not having been provided for, I concluded after a full consideration of the subject that the interest of the Company would be best promoted by so altering the organization as to abolish it altogether, and extend the eastern and western divisions to the summit of the Allegheny mountains, the natural boundary between them. Under this arrangement, the surveys have since been prosecuted.

The Board having directed me to cause a location of the whole line, from Harrisburg to Pittsburg, to be made at the earliest practicable period, I at once commenced a reconnoissance of that portion of the intervening country, over which it seemed—from an inspection of a map of the State—that the Road would probably pass, for the purpose of determining the best plan of operations to carry out their views.

The Legislature, in their grant to the Company, wisely left the choice of a route for the Road, between its termini, entirely free, throwing upon the Board the responsibility of selecting, upon the wide field that was opened to them, a line for their great work, which would offer the cheapest railroad conveyance for the transportation of freight and the most expeditious for travel that could be selected between the west and the northern Atlantic cities.

Such a route, it was believed from previous surveys, lay within the borders of Pennsylvania, an expectation which has been fully justified by the results obtained from our examinations.

Of the several routes proposed, I found no difficulty—after a careful inspection of the plans of the various surveys, made under the authority of the Commonwealth, and my reconnoissance of the country—in coming to the conclusion that the valley of the Juniata offered advantages for a line which, whether we consider the low gradients that may be obtained along it or its general directness, the desiderata required, is without a rival.

This stream has its source in the Alleghenies, and consequently severs, as it flows towards the Atlantic, all the secondary mountain ranges that lie east of them, and it heads opposite to the Black Lick and Conemaugh rivers, both of which sever those on the west, leaving the main Allegheny only to be surmounted, which would have to be encountered upon any other direct route, in addition to many of the inferior mountain ranges. A more northern route, by the west branch of the Susquehanna (which has its source beyond the Allegheny mountains), would have encountered less elevation at the principal summit, but its great increased length precluded its adoption; while, on the other hand, a southern route, though not indirect, was equally objectionable on account of the rugged character of the country, and the high gradients necessary to overcome the numerous summits upon it. A partial examination of one of the proposed southern routes was made, which followed the Cumberland Valley Railroad to near Shippensburg, and thence, crossing to the west side of the valley at Roxbury, it passed through the Blue Mountain, by a long tunnel, into Path valley; thence, following around the point of Dividing mountain, it crossed this valley and passed through Tuscarora, by another tunnel, to the valley of Augwick creek. Thence it would have been traced between Broad Top and Sideling mountains, and up Dunning and Bob's creeks to the summit of the Alleghenies at Bob's Creek gap; or, turning west by Bedford, crossed the Alleghenies at the head waters of the tributaries of Castleman's river, where the mountain is still much more elevated.

A line leaving the Cumberland Valley Railroad at Chambersburg, and turning the end of Blue mountain, thence seeking the low depression at Cowan's gap in Tuscarora, would be too circuitous to compare favorably with the bolder line from Shippensburg, already described.

But that line would encounter engineering difficulties of the most formidable character; leaving out of view its objectionable gradients, and considering it in reference to its cost, and the local accommodations it would extend to a large portion of the State—at present in a great measure deprived of the advantages of the State improvements—(the strongest argument in favor of the route), it will be found that equal accommodations could be extended to that region with a less expenditure of capital by placing the main stem of the road on the Juniata, and running a branch along one of the comparatively level valleys that lie between most of the parallel mountain ranges that we pass.

The facilities that railroads offer for extending their benefits to remote districts by means of lateral lines constitute one of their chief advantages over canals, and should prevent the error, too frequently committed in locating leading routes, of turning from a direct course to accommodate local interests to the injury of the great object intended to be accomplished.

Other modifications of the Juniata route have been suggested, and their merits fully considered, but, upon examination, all of them tended to confirm our preference in favor of the river line.

These conclusions were communicated to the Board, and the general route recommended having been adopted by them, I proceeded at once to make arrangements to have the line surveyed throughout. For this purpose three additional corps of engineers were organized—one for Mr. Miller's division, under the immediate direction of Mr. G. W. Leuffer, to operate on the summit and western slope of the mountain, and two upon Mr. Foster's, the first of which was placed in charge of Edward Tilghman, Esq., to whom was assigned the district between Lewistown and the confluence of the Raystown branch and main Juniata rivers.

The other corps was given in charge to S. W. Mifflin, Esq., a gentleman of well-known professional skill and experience, to whom we committed the surveys of the region from the Raystown branch to the summit of the Alleghenies, embracing the 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 F: Relative load of locomotive on each gradient,

level being unit.

Col G: Number of locomotives of equal power necessary to carry

the same load up each gradient.