302 HISTORY OF ENGINEERING. Book I.
were then laid down; and the II rail in 15 feet lengths was adopted; the weight ofwhich was fifty-five pounds per yard.
The Boston and Worcester line is in length forty-four miles, and has several deep cuttingsand high embankments; where it crosses the Charles river is a viaduct of masonry andtrestle work. The rail used is that of the T form, weighing about 38^ pounds to the yard.The bars are about 15 feet in length, carried by iron chairs, weighing about 15 pounds each ;they are tightened by means of two wrought iron keys.
The chairs are placed on sleepers of cedars 5 inches square, and in lengths of 7 feet; theseare laid crossways at regular distances of 3 feet from centre to centre, and bedded on piersof rubble masonry; this was, however, found insecure, and a longitudinal under sill ofchestnut 8 inches by 3 inches has been added throughout.
The Western railroad, extending from Worcester to the valley of the Hudson, is in lengthmore than 11 (5 miles; and the four summits are from 900 to 1500 feet above the level of thesea. The width of the track is 4 feet 8J inches ; the rails are of a parallel form, 3£ inchesin depth, 4 inches on the base, and 2 inches at the top; the weight is fifty-five pounds peryard. They are laid upon sleepers of chestnut, 7 feet in length, 7 inches in depth, and12 inches wide. These sleepers rest upon others of hemlock wood, laid longitudinally,8 inches in width, and 3 inches thick, so placed, that they measure 4 feet 10 inches fromcentre to centre ; where the joints of the iron rails occurs, there are four cross-timbers, 3 feetin length.
The rails are kept in their place in the usual manner, and the chairs are spiked into thesleepers.
The maximum inclination is 60 feet in a mile, and the minimum radius of curvature1146 feet.
The Boston and Providence line is in length 41 miles, and the least radius is 5730 feet;the highest inclination is 25 per mile in the direction towards Boston , and on the other side37 feet 6 inches ; the highest elevation is 256 feet above the level of the sea.
The Granite Viaduct at Canton is 700 feet in length, and where it crosses the Neponsetriver is 60 feet in height. The wooden bridges on this line are 1200 feet in extent, andtheir spans vary from 30 to 125 feet.
The rails are of the II pattern, in lengths of 15 feet, weighing 55 pounds per yard.The iron chairs weigh ten pounds each, and are only used where the rails join each other;they are let into the sleepers, and secured by four spikes. The rail is fastened by broadspikes, four on each sleeper; 6 inches in length, half an inch square, and weighing nineounces each. There are cross ties of white cedar under the rails, laid 3 feet from centre tocentre.
Providence and Stonington railroad is 47 miles in length, has rails of the H pattern, inlengths of 15 feet, weighing fifty-eight pounds per yard, with square ends. The cast-ironchairs weigh ten pounds each, and are spiked down to the sleepers, with spikes nine ounceseach. The sleepers of white cedar are laid 3 feet apart, arc 7 feet in length, and 6 inchesin thickness; they rest on sills of hemlock, 8 inches by 3 inches, and where the joints occur,there are additional piers 5 feet in length laid under them.
The highest elevation is 302 feet above the level of high water, and the maximum risenot more than 33 feet in a mile ; the minimum radius of curvature 1637 feet.
Norwich and Worcester railroad is in length 58£ miles; its maximum grade is 20 feet permile, and the average inclination is 11 feet per mile.
Long Island Railroad is in a state of progress, and one portion of the line rises 200 feetin a mile. The other gradients do not exceed 40 feet in a mile, and the minimum radiusof curvature is 5280 feet. The rails are of the T pattern, weighing thirty-eight poundsper yard, resting on cast-iron chairs; these are confined on stone blocks, placed on crossties of timber. The sleepers are of red cedar, in lengths of 8 feet, and 6 inches square.The iron chairs weigh fifteen pounds each when they are placed on the sleepers, andtwenty pounds each on the stone blocks. An iron tie crosses the road, and holds theopposite stone blocks together ; it is a bar of half an inch thick, 2| inches in width, and4 feet 8£ inches in length.
The top part of the rail rests on the chair, and is secured by a double key.
Harlem Railroad, twenty-six miles in length, is a double track, and is travelled forthree-fourths of its length by steam power.
The tunnel through which the line passes is cut through a solid rock, composed ofquartz and hornblende, of so compact a nature that masonry was unnecessary. It extends844 feet, and is in width 24 feet, and 21 feet in height. On this road the plate rail is laiddown; it is 2J inches in width, and five-eighths thick; it is secured to longitudinaltimbers 77 feet long, laid across ties of locust and cedar, placed 3 feet 6 inches apart.
New York and Albany Railroad at one point attains an elevation of 770 feet, but thegradients seldom exceed 30 feet per mile. The length of this line is 147| miles, and theradii of curvature is seldom above 1500 feet.
Camben and Amboy Railroad, in length sixty-one miles; the radii of its curves are