304
HISTORY OF ENGINEERING.
Book I.
then sills of chestnut and white oak were laid down, in lengths of 7 feet 6 inches, and 7 inchessquare, notched, to receive a yellow pine string piece, 6 inches square, which is spikeddown securely. On this are the flat iron bars, and the horse-way is formed as beforedescribed.
Edge Rails on Stone Blocks and Sills —Trenches were dug in the direction of the length ofthe road, 28 inches wide, and 24 in depth ; at every 15 feet these were connected by across-trench, 16 inches in width: broken stones were rammed into them, and blocks andsills were settled by the means of heavy rammers. The granite blocks are 20 inches long,16 wide, and 12 deep. The sills, also, of stone, 6 feet 6 inches long, and 12 inchessquare, are sunk in the trench at every 15 feet. The rails have a bearing on the blocks atevery 3 feet. The chairs, which are of cast-iron, weigh 15 pounds, and are secured to thesills and blocks by bolts driven into cedar plugs inserted in the stone. Each chair has twobolts, weighing 10 ounces each, and between the chair and stone block is a piece of tarredfelt. The rails are of rolled iron, 15 feet in length, parallel top and bottom; their depth is3$ inches, and their weight, per yard, 41$ pounds. The rail is fastened to the chair bytwo wrought-iron wedges, each weighing 10 ounces. The horse-path is similar to theothers.
Edge Rails on Stone Blocks and Locust Sills —The locust sills are 15 feet apart on the straightlines, and 9 feet on the curves, and the remainder of the work is the same as the edge-railtrack already described.
There are turn-outs for the horses at certain intervals. On this line of railroad all thebars used belong either to individuals or to companies, whilst the motive power is foundby the state.
The locomotives run daily about 77.miles.
There is an inclined plane at the Philadelphia end 2714 feet in length, and rising 185feet. Another at Columbia is 1914 feet in length, and rises 90 feet. The cars are movedup and down by a stationary engine of 60 horse-power, and an endless rope 9 inches incircumference, which passes round horizontal grooved wheels, placed at the top and bottomof the planes.
Allegany Portage Railroad , its length is a little more than 36$ miles, and its total rise andfall 2570 feet, of which 2007 feet are overcome by planes, the inclination of which variesfrom 4° to 5$°, or from 7$ feet to 10$ feet, for every 100 feet base. They are all straight,both on plan and section. The total length of their base is a little more than 4$ miles ;the rest of the gradients are about 15 feet per mile. All the embankments are 25 feet inwidth ; at the top there are four viaducts of considerable extent: that over Conneinaugh isa single arch of 80 feet span, the top of the stone work is 70 feet above the surface of thewater; there are 68 culverts, 85 drains, several bridges, 10 inclined planes, 11 levels, andone tunnel, 901 feet in length, 20 feet wide, and 19 feet in height to the soffite of the arch.
The edge rails are parallel, and made of rolled iron, weighing 40 pounds per yard ; theyare supported bv cast-iron chairs, weighing 13 pounds each, and the rail is secured in themby an iron wedge. The stone blocks under them contain each about 3 feet 6 inches of cubestone, and are placed on a bed of broken stone, at a distance of 3 feet from centre tocentre. At the head of each inclined plane are two stationary engines of 35 horse-powereach, which work an endless rope, and can draw up four cars loaded with 7000 poundsweight, and let down four at the same time ; from six to ten changes can be made in anhour. A safety car is in attendance in case of any accident occurring to the rope.
In the formation of this railroad there were
337,220 cube yards of common excavation.
212,034 - - slate or detached rock.
566,932 - - hard pan or indurated clay.
210,724 - - solid rock.
14,857 - - solid rock in the tunnel.
967,060 - - embankments carried over 100 feet.
67,327 perches slope wall.
13,342 - - vert and wall in drains.
Philadelphia and Reading Railroad is 59 miles in length, and in one instance the gradientis. 19 feet to the mile ; the others vary from 18 inches to 11 feet in the same distance, thereare three tunnels on the line.
The H rail is used; the weight is 45 pounds 2 ounces per yard ; the lengths are 18 feet9 inches, with square ends. About eight of these lengths weigh a ton ; the sleepers uponwhich they are secured are of white oak, laid transversely about 7 feet in length ; they arebrought to a face on the under as well as upper side, in order that a true bearing might beobtained throughout; they are 7 inches in depth, and laid at a distance of 3 feet 1$ inchesfrom centre to centre. Under them is a foundation of broken stone, in a trench excavatedto the depth of 14 inches, and in width 12 inches; the length was 2 feet more than that ofthe sleepers bedded on them. After these walls were laid, and the timbers placed, thespaces l>etween them were filled up level with clay, or any other material at hand. The