CHAPTER II.

HOW A RAILROAD IS BUILT.

How little the railroad traveller, thoughtful only of speed, comfort, and cheapness, sees of the formidable works over and through which he is so safely and rapidly carried! How little he knows of the herculean labors that have been performed, the anxieties that have been borne, the skill and invention that have been brought into exercise, the desperate difficulties that have been surmounted, in order to provide for him those two parallel lines of iron over which he smoothly glides and peacefully snores. Yet for boldness of design, skill in construction, and success in completion, the gigantic achievements of engineering performed in the laying of great railroads, greatly surpass in magnitude as well as in utility, those that have left their own monuments from earlier ages.

The main object of the railroad engineer is to reduce his road as nearly as possible to a level. High grounds are to be cut down, and embankments raised across the lower lands. When a mountain intervenes, through which an open cut is impracticable, the expedient of a tunnel has to be adopted. When a deep valley lays in the way, and an embankment is not feasible, then there must be a viaduct. And when an arm of the sea, such as the Menai Straits, has to be

crossed, it must be overleaped on iron tubes swung in mid air. Of the eight thousand and fifty-five miles of railroad in operation in England six years ago, seventy miles passed through tunnels, and more than fifty miles over viaducts; while of railroad bridges there had been built some three thousand large and costly structures.

Incredible difficulties have been encountered by engineers in carrying embankments of earth across low grounds. These grounds, in many places, under a fair, green surface, have been found to conceal the remains of ancient bogs and swamps, sometimes of great depth. Thus, on one English railroad, about six hundred tons of stone and earth were daily used to form an embankment across a valley, and morning after morning, for many weeks, the material deposited on the preceding day was found to have disappeared. A still more remarkable instance, however, is said to have occurred on a road in the United States, where an embankment, which had been entirely constructed, suddenly disappeared from view, and was found to have sunk in thirty feet of water. The cause of this was ascribed to the fact that an extensive lake had, in the course of ages, been covered with various deposits, which at length formed a soil of sufficient stability to withstand the operations of agriculture without giving way; but being oppressed by the weight of so extraordinary a contrivance as a railroad embankment, it declined to be thus burdened, and sunk at last beneath the waters.

The Michigan Southern Railroad, to fill a "sink hole" of forty rods under its track in Northern Indiana, has

dumped in two acres of earth averaging ten feet in depth; three acres of timber and brushwood; the ditchings and scrapings of fifty miles of railroad track for about eight years past; the old ties of about one hundred miles of repaired track; and about three thousand car-loads of gravel; besides the forty rods of embankment, from four to six feet high, that were made before the sinking occurred. The work of filling seems now to have been accomplished.

TUNNELS.-In Chester County, England, the great Woodhead tunnel penetrates the mountain for a length of about three miles, under a dreary, barren moor, undisturbed save by the sportsman's gun. The usual shafts were sunk over the line of the tunnel, down towards its base. The average depth of the shafts was six hundred feet-but it was long, indeed, before the workmen could reach the bottom level. The sinking, blasting, and winding went on so slowly, that the tunnel was six years in progress. This was caused by the hardness of the material, and the immense quantity of water that flowed into the shafts. The operation of pumping continued incessantly for five years, during which time the engines brought up no less than eight millions of tons of water. At two of the shafts, where continuous pumping was kept up, not an inch was gained in nine months. In another, it took eleven months to sink fourteen yards. The water was never entirely conquered, until the under drift was blasted through the line of the tunnel, whereby the upper springs were tapped, and the water flowed out of the open end of the tunnel by its own gravity. The blasting in this tunnel was on so

enormous a scale, that not less than three thousand five hundred barrels of gunpowder, weighing about one hundred and sixty tons, were used in the operation.

More gunpowder, indeed, has been expended in railroad works than has been blown away in the recent Civil War in America, with the Crimean War added. Near Dover, in England, Sir William Cubit, in 1833, blew away, with one charge of nineteen thousand pounds of gunpowder, the entire mass of the Round Down Cliff, which rose to the height of three hundred and fifty feet above the level of the sea This terrible blast, fired by galvanic electricity at several points instantaneously, at once hurled off from the cliff a mass of more than a million tons of chalk, which rolled down upon the beach-the dislodged masses of chalk covering and whitening a space of more than fifteen acres, as may still be seen, stretching towards the sea near the western base of the wellknown Skakspeare's Cliff.

By means of a similar blast, on the Londonderry and Coleraine Railway, a hill was thrown into the sea by a charge of three thousand pounds of gunpowder; and thirty thousand tons of material were thus instantaneously removed from the line of the works.

A delicate piece of tunnel surveying and underground building was executed at Glasgow, in Scotland, where the Garnkirk Railroad passes, by means of a tunnel four hundred feet long, under the Monkland Canal, and over the tunnel of the Edinburgh and Glasgow Railroad. The two tunnels stand secure, tier over tier.

In Derbyshire, England, Mr. George Stephenson carried a railroad over a bridge which there spanned the river Amber, and at the same point, under the aqueduct of the Cromford Canal. River, bridge, railroad, and canal, were thus piled one above the other, four stories high. Such another curious complication in railroad engineering probably does not exist.

AMERICAN TUNNELS.-Most of the tunnels on American roads are on the lines crossing the Alleghany Mountains. Through the main Alleghany ridge, near its summit, a tunnel was completed in January, 1854, for the Pennsylvania Railroad, the length of which was three thousand six hundred and twelve feet, the width twenty-four feet, and the height twenty-two feet. To expedite the work, and facilitate the removal of the rocky material, four shafts were sunk, from the surface down to the level of the tunnel. One of these was thirteen feet wide, the others were ten feet wide. These shafts varied in depth, being one hundred and fifty, one hundred and fiftyfour, one hundred and ninety-six, and one hundred and ninety-four feet deep respectively. The rocks were found to be the nearly horizontal strata of the coal measures, the tunnel in great part lying along a bed of fire clay, which, though easily excavated, caused considerable expense and much trouble in properly securing the walls and roof. The work was completed in two years, at a cost of nearly half a million of dollars ($450,000).

Many fine tunnels are found on the line of the Balti more and Ohio Railroad, particularly on the Parkersburg branch. On the main stem of this road, the