Chap. VII.
SOI
From Baltimore to Wheeling , 280 miles, the canal and railroad extend throughout; andthe same kind of communication exists from Richmond, in Virginia , to Covington and theOhio river . From Charlestown to Louisville , Cincinnati , and the Ohio , the line, whencomplete, will be upwards of 700 miles.
The great Atlantic line is considered the main trunk to which all others seem united ;the western states are carrying out lines of railroads and canals of not less than 2000 milesin length.
The first lines laid down were with iron rails and chairs, on stone blocks, which werefrequently so split by the frost, that it was necessary to remove them ; the rails also becamederanged, and extremely dangerous for the passage of carriages. Numerous methods havebeen adopted in the states to remedy the inconvenience arising from the great changes oftemperature, as will be seen in this brief account of their railroads. The usual breadth be-tween the rails is 4 feet 8^ inches, and when two lines are laid down, the distance maintainedbetween them is usually 6 feet.
In the southern states, where a line is carried over low and marshy ground, and a diffi-culty is found in obtaining earth to construct the embankments, a series of timber trussesare substituted, which often rise 10 or 12 feet above the level of the plain ; on these thelongitudinal timbers are laid to carry the rails. Piles of from 14 to 16 inches in diameter,not sharpened, are first driven in, forming two lines the width of the way; when these areperpendicular, inclined struts are placed on the outside, which passing at the upper endunder the transverse timbers, and abutting at the lower upon another short pile, renderthe woodwork tolerably secure.
Another method is to drive four slanting piles, two one way and two the other, eachpair uniting at top under the longitudinal timbers, and in the middle of the width at bot-tom, where transverse binding pieces are firmly bolted to them, and secured either byadditional piles or cross sleepers. Occasionally a double series of St. Andrew’s crosses areused, but they have generally been found subject to considerable movement when in con-nection with the locomotive engine.
The cost of the American railroads is considerably less than in England: many of thesingle tracks have not exceeded 4000/. a mile, and, including buildings and all requisiteapparatus, the average expense does not seem to exceed 20,000/. per mile.
One system frequently adopted seems extremely economical sills of white oak 7 feet10 inches long, and about 9 inches in depth, are laid across the road, at a distance of 5 feetfrom .centre to centre; and notches are cut at the ends, into which are laid longitudinalpieces of heart of pine wood, 9 inches in depth, 5 inches in width, and 4 feet 7 inches apart.On their inner edge, plates of rolled iron 2 inches wide, and half an inch thick, are spikeddown with wrought iron spikes, 5 inches in length ; and where the plates form a junction,there is an additional plate of sheet iron one-twelfth of an inch in thickness; this system isfound to answer when the locomotive engines are from fifteen to twenty horse power, andthe cost per mile in America does not exceed 600/. The locomotive engines, when theirboilers are filled, seldom weigh more than 15 tons, and their driving wheels are placed in thefore part near the fire-box ; they are 5 feet in diameter; the front of the engine runningon four wheels, half the diameter of the large ones.
On the truck which runs on the fore wheels are a number of friction rollers, placed in acircle, in the centre of which is a vertical pivot, working in a socket of the frame-workwhich supports the engine. The friction rollers support the cylinder and part of theboiler, and the truck of the carriage acting on the pivot oescribes a portion of a circle,which is of great service when the engine is not running on a level road ; at each side ofthe engine a guard is usually attached to prevent it being thrown ofT the rail; this isnothing more than a strong piece of timber, fixed to the front axle, and supported by twowheels, of 2 feet in diameter, which run on the rails a few feet in advance. This piece oftimber is on the outside, shod with iron, slightly bent upwards, which clears away any ob-struction that may be offered to its progress.
The Boston and Lowell railroad is in length about 26^ miles; it has eighteen viaducts,one of which is 1600 feet in length, and fifty-one bridges. The maximum rise is l in528, or 10 feet per mile, and the least radius of curvature is 3000 feet.
Where the line approaches Lowell, the cutting for 1000 feet is through the solid rock,which at the top is 60 feet in width, at the bottom 40 feet, and the mean height the same.At the commencement fish-bellied edge rails, weighing thirty-five pounds per yard, on cast-iron chairs, were laid down. The chairs were fitted on stone blocks, which rested on stonecross sills ; the bearings were about 3 feet from centre to centre, and the blocks and sillswere carried throughout by a longitudinal wall constructed of rubble, laid dry, 3 feet inheight, 2 feet 6 inches wide at the footing, and 2 feet at the top. The space between thesewalls was packed in with clay, and other earth that could be easily obtained.
The construction not being found to answer, the foundations have since been laid in withsand and gravel; a trench being opened for its reception, 3 feet in depth, and 7 feet inwidth, it was well rolled and rammed; sills of stone, 6 feet in length, and 12 by 6 feet