Chap. VII.
803
about 1800 foot, and the usual gradients 20 feet per mile. The rails are the II pattern,in lengths of 16 feet, weighing forty-one pounds per square yard. The rails are supportedon stone blocks, 18 inches square, and 12 inches in depth, placed in a continued trench, atregular distances. Where the rails join, there are cast-iron plates spiked down belowthem, which, by means of a notch cut in the rail, prevent its moving endways; the railsare attached to each other at the ends by an iron plate 4 inches in length, which is rivetedto each rail; the rivet has a play to allow of contraction and expansion.
On the top of the stone blocks is a piece of wood 2 inches in thickness, to adjust theplacing of the rail.
Wherever the clay occurred, it was taken out, being so readily affected by frost, sandand gravel being substituted.
New Jersey Railroad , thirty-four miles in length, has its least radius of curvature2000 feet, and the steepest gradient 26 feet per mile. The rails are of the T form, andweigh thirty-seven pounds per yard; they are in lengths of 18 feet, with square ends.The rail rests upon its two upper flanches on chairs, a single key keeping it in its place.The chairs weigh fifteen pounds each, and are placed at equal distances, measuring 3 feetfrom centre to centre; they are secured to cross sleepers of cedar wood and chestnut.
There are two timber viaducts, one over the Possaic, the other over the Hackensack,which are worthy of notice.
At Bergen Ilill is a deep cutting, a mile in length, and at one part 50 feet in depth,35 feet of which is through hard rock ; more than 500,000 cubic yards were excavated.
The. Viaduct at Ilaritan is on the plan called after Colonel Long; its length is 1700 feet,and its spans vary from 112 feet to 145 feet; the depth of the truss being 22 feet, andthe width between the rails at the top 31 feet. There are seven piers and two abutments,faced with granite, and filled in with blue and red shale stone; this viaduct lias two storiesin height; the lower floor is supported by trusses, and a double roadway is carried bymeans of joists laid 4 feet apart. The chairs that confine the rails rest on strong pieces,11 inches in width and 4 inches thick, pinned down to the floor at top, which serves as aroof. The braces of the truss-framing abut upon thin plates of sheet iron.
Parts of the floors draw up, to allow the passage of vessels at certain appointed times.
Columbia and Philadelphia railroad is 8l£ miles in length ; the maximum gradient is 30feet per mile, and the minimum radius of curvature 631 feet. The deepest cuttings arebetween 30 and 40 feet, and the highest embankment is 80 feet.
There are 75 stone culverts, varying in span from 4 to 25 feet, 20 viaducts, the piersand abutments of which are stone, the structures above of timber, and 33 bridges.
The Schuylkill viaduct is of timber, formed into distinct trusses, the whole width, fromout to out, being nearly 50 feet, which is sufficient to allow three separate ways, two of 18feet 6 inches, and the other of 4 feet for foot passengers. There are six piers and sevenspans; the whole length of the viaduct is 1045 feet; the height of the floor above the water-line is 38 feet.
Valley Crqek viaduct has four equal spans of 130 feet clear, and the stone piers vary inheight from 56 to 59 feet. The woodwork consists of a lattice bridge, with the railwaycarried over the top.
Past Brandywine viaduct has four spans, two of 88 feet 6 inches, and two of 121 feet 6inches. The clear width is 18 feet 6 inches, and the whole length of the platform 477 feet,the clear height above the water 30 feet.
The West Brandywine viaduct has a platform 835 feet in length, which is 72 feet abovethe water; the line is carried over the top of the framing.
Big Conestoga viaduct is in length 1412 feet, the platform is 60 feet above the water.The greatest span is 120 feet, and the lattice timber-work is upon Town’s plan.
Little Conestoga viaduct has also stone piers and abutments, the length of the platformis 804 feet, and its elevation above the water 47 feet.
Mill Creek viaduct is 540 feet in length, and is 40 feet high.
Peguea viaduct is a single span of 130 feet, it is in timber, on the plan of Mr. Burr.The length of the single track is 163 miles, six miles of which have granite sills, on whichare flat iron bars; 16 miles with wooden string pieces, plated in a similar way withiron; two miles with stone blocks, and sills with edge rails; and 137 miles, with stoneblock and edge rail, with timber sills across the track.
The granite track has trenches cut in the line of its direction about 22 inches in depth,into which is compactly placed layers of broken stone. Granite sills are then laid, varyingin length from 3 to 12 feet, and 12 inches square; into these holes are drilled five-eighths ofan inch in diameter, and 3£ inches in depth, into which plugs of.locust wood were securelydriven. The iron bars, 15 feet in length, 2^ inches wide, and five-eighths of an inch thick,are spiked to these wooden plugs. As horse-power is used, there is a pathway of brokenstone and gravel 6 inches in depth.
The timber track _Trenches were dug across the road 4 feet apart, 8 feet in length, 12
inches wide, and 16 inches in depth ; broken stone was thrown into them and well rammed,