ON the morning following Christmas-day, 1870, a telegram was received in London from the very heart of the Alps; thence it was dispatched across the Atlantic, and in the gray dawn of the next day, December 27, we read it at our breakfast-tables in New York. This dispatch of just forty-three words read thus:

"The working parties in the opposite headings of the Mount Cenis Tunnel are within hearing distance of each other. Greetings and hurrahs were exchanged through the dividing width of rock for the first time at a quarter past four o'clock on Christmas afternoon."

This brief dispatch, almost overlooked among the more exciting ones relating to the war-for the opening of the bombardment of Paris was hourly expected—conveyed tidings of the practical completion of the most enduring work ever accomplished by human bands. The Pyramids will, in time, crumble to dust; but nothing less than some convulsion that shall shatter the Alps from summit to base will destroy the Mount Cenis Tunnel.

Perhaps the point of view from which this Alpine tunnel is of most commercial importance is that it shortens the distance—measured by the time required to traverse it, rather than by the space passed over—between Western Europe and India. This will appear from a glance at the accompanying map. At present mails and passengers by the overland route from London to India proceed—by way of Calais and Lyons—to Marseilles, where they embark, and, after passing through the stormy Gulf of Lyons, rounding the toe of the Italian boot and the island of Sicily, reach Alexandria, or, more recently, the mouth of the Suez Canal, in Egypt; whence, descending the Red Sea, they cross the Arabian Gulf, and land at Bombay; or, rounding the peninsula of Hindostan, they enter the Bay of Bengal, and are disembarked at Madras or Calcutta. The entire distance from London to Alexandria, by way of Marseilles, is 2534 miles, of which 833 are traveled by land and 1701 by water, the whole journey occupying seven or eight days. Ten or twelve miles an hour is a fair rate for ocean steamers, whereas forty miles an hour is usually made by express trains on a railway. If, therefore, any considerable part of the 1701 miles of sea voyage between London and Alexandria can be performed by railway, there will be much saving in time.

Now, again looking at our map, it will be seen that, starting from near the head of the Gulf of Genoa, the boot-like peninsula of Italy stretches for 600 miles from northwest to southeast, pointing directly to the coast of Egypt. It forms a natural bridge half-way across the Mediterranean, in the direct route from London to Alexandria. Close by the southeastern verge of Italy—almost at the heel of the boot—is Brindisi, the ancient Brundisium, of which all readers of Horace know something; for the Iter ad Brundisium ("Trip to Brindisi") is one of the cleverest poems of the old Roman good-fellow. Any one who desires to post himself up about Brindisi, from the time when Ennius, almost forgotten when Horace lived, punningly presents it as pulchro proecinctum proepete portu ("properly placed with a pretty port"), and how Caesar put Pompey out of this pretty port, can find it all told in his Anthon. Here, also, was the terminus of the famous Appian Way, the spot being to this day marked by two pillars, one sadly dilapidated. Virgil had here a country house, the ruins of which are yet shown; and there axe not wanting those who put faith in their authenticity.

Some day, as a glance at any fair map will show, there will be two good routes from Europe to India: the one mainly by railway on land; the other a considerable part by water. The former, leaving England at Dover, and crossing the English Channel to Calais or Brussels, will traverse Belgium, Germany, Austria, and what is now known as Turkey in Europe, reaching the Bosphorus not far from Constantinople. Thus far the route runs entirely overland, avoiding the Mediterranean and its long gulfs, and also skirting the Alps on their northern face. The trains, without breaking up, will be ferried across the Bosphorus (more properly Bosporus, "a strait over which an ox can swim," the exact Greek for our "Ox-ford"), Thence crossing Asia Minor, or, as we now call it, Turkey in Asia, the railway will round the southern end of the Caspian Sea, passing through Persia and Afghanistan to the Indus. Thence running across the head of the peninsula of Hindostan, it will reach Calcutta. This route, after leaving the Bosphorus, is, as far as the Indus, just that followed by Alexander the Great in his famous expedition to India—by far the most, remarkable military march ever performed. The second route, branching off at the crossing of the Bosphorus, will follow the eastern shore of the Mediterranean to Syria; thence, crossing the Lebanon range, it will strike the valley of the Euphrates, which it will follow to the head of the Persian Gulf, down which it will descend by steamer, crossing the head of the Arabian Sea to the mouth of the Indus, where it will again strike the railroad route across the Indian peninsula to Calcutta. This second route, from the mouth of the Indus to the upper waters of the Euphrates, is the one followed by Alexander on his return from India. The great Macedonian, more than two thousand years ago, showed the two ways from Europe to India.* But these routes will not practically exist until the long-vexed, and still to be vexed, Eastern question gets itself somehow settled. For the present, and for another generation, we must consider the overland route to India as running through Italy. And to this route the Alps interpose a barrier which will be, in a measure, overcome by the Mount Cenis Tunnel.

* Any ordinary map of Southern Asia will show with tolerable accuracy the two Indian routes of Alexander, followed by him on his advance and return. The main points to be observed are: for the overland route, the Bosphorus, the southern end of the Caspian Sea, and the River Indus; for the return route, the mouth of the Indus, the Persian Gulf, and the valley of the Euphrates. In the twelfth volume of Grote's "History of Greece" is an admirable map, showing the whole of the marches of Alexander. It is not impossible that Russia may anticipate the whole of this scheme by a railway which, leaving the mouth of the Volga, shall skirt the northern end of the Caspian, and run southward and eastward through Tartary and Afghanistan to the Indus. Whichever, Russia or Great Britain, first reaches the Indus by a railway route will be the master of India from Ceylon to the Himalayan Mountains.

It must not, however, be understood that the Italian government had any such extended views in projecting the tunnel through-the Alps. It proposed simply to facilitate travel between France and Italy, or rather between its own province of Savoy, lying on the northern side of the Alps, and the remainder on the southern side of the mountains.*

* In 1860 the provinces of Savoy and Nice were ceded by Italy to France, in exchange for portions of Lombardy, wrested from Austria. The tunnel, which had been commenced by Italy, was to be completed, under Italian superintendence, at the joint cost of France and Italy. As the map now exists, the northern end of the tunnel is in France, the southern in Italy, the summit of the Alps being the boundary between the two countries.

The Alps—using the term in its widest sense—is that remarkable chain of European mountains which forms the water-shed dividing the rivers which empty into the Mediterranean from those which fall into the Atlantic, the German Sea, and the Black Sea. The whole length of the ridge is about 1100 miles, besides numerous spurs or offshoots, such as the Apennines, the Pyrenees, the Carpathians, and the Balkan. Generally, however, the term is restricted to much narrower limits, and denotes that mountain chain which, commencing near the head of the Gulf of Genoa, curves northward to Mont Blanc, and thence northeastward through Switzerland, the Grisons, and the Tyrol in Austria, where it terminates in the Great Glockner, "Bell Tower." This range, sometimes styled "The Higher Alps," measures about 420 miles. In parts it consists of a single steep range; elsewhere, notably in Switzerland, there are several parallel ranges, scarcely less lofty than the main ridge. The loftiest peaks are in Switzerland, where, within a space of not more than sixty miles, are the highest points in Europe—Mont Blanc, the loftiest of all, reaching an elevation of 15,744 feet above the level of the sea. From this central point the mountains fall away gradually in either direction. But still the height of the ridge, not counting the more elevated peaks, is about 7000 feet. In our sense of the word there are no "passes"—that is, deep depressions cut down through the great mountain wall. Whoever crosses it must ascend about 7000 feet. Nineteen "passes" are, indeed, enumerated; but of these eight can only be traversed by foot passengers, and now and then by mules. Over the remaining eleven there are carriage roads; but there are not more than five that are fairly passable for carriages; and for three of these roads the world is indebted to Napoleon.

The one pass with which we have now to do is that which leads near but not over Mount Cenis. Near the centre of the great northwestern curve of the Alpine chair rises Mount Cenis. It is by no means among the loftiest of the peaks. Its summit is four-fifths of a mile lower than that of Mont Blanc, and it is overtopped by nearly a score of other peaks. Still it dominates over all its immediate neighbors, rising to an altitude of 11,454 feet-nearly twice that of any point in the United States east of the Rocky Mountains. From the peak the summit of the chain sinks down northward into a long col, or "neck," the lowest point of which is 6672 feet high—about 400 feet higher than the summit of Mount Washington. This neck is what is styled the Pass of Mount Cenis.

This possible pass from Gaul to Italy appears to have been unknown to the ancients. Hannibal, two centuries before Christ, went directly past it, for forty miles, crossing the Alps at the Little Saint Bernard, losing on the way 33,000 out of the 59,000 men with whom be started. The first authentic mention of the Mount Cenis pass is a thousand years later, when (about A.D. 755) Pepin led his army across it, to aid the Pope against the Lombard king. Half a century later his son Charlemagne led another army, for the same purpose, over the same route. To this day there stands, almost at the summit, a hospice, said to have been founded by Charlemagne. In 1557 the Duke of Alva led his Spanish army over this pass for the subjugation of the revolt in the Netherlands. A century later Marshal Catinat led a French army into Italy over this pass. During these centuries the roadway had been somewhat improved, but it remained little better than a mere mule-path until 1803, when Napoleon conceived the idea of making a carriage road over the pass, to form a means of communication between France and Italy, then united under his sceptre. The work, occupied seven years, and was the most marvelous engineering achievement hitherto accomplished. It was a highway, eighteen feet broad, excavated for a great part of the distance in the sides of the mountain. Taking its two proper terminal points, San Michel on the western side, and Susa on the eastern, the distance in a straight line is about thirty miles; but following the windings of the road, it is fifty. In that space the road ascends and descends about 5000 feet, say a mile of absolute elevation and descent. The mode of travel was by diligence, sixteen mules being required to drag a carriage up the steepest ascents. In the winter the carriages were frequently placed upon runners instead of wheels. More than half of this perpendicular ascent and descent had to be performed within what in a straight line would be about eight miles.

For forty years this Napoleonic road seemed the only practicable way of crossing the Alps at this most available point. But meanwhile railways had been pushed up to the foot of the mountains on either side. But no one for years seems to have dreamed that this sharp ascent, sometimes amounting to a rise of one in twelve, could be overcome by any engine moved by steam-power. The problem lay in this shape: the moving power of a locomotive is simply the amount of the traction of the driving-wheels upon the rails. Upon a straight course, an ascent of one foot in a hundred produces a sensible effect; one in fifty is a grade so heavy as to diminish the effective power of the engine by half. At one in twenty-five the power is practically nothing; a locomotive train attached can barely overcome it. A little steeper, and the driving-wheels will only revolve upon the rails, without moving the locomotive at all forward. Arise of one in thirty is about the utmost practically overcome by an engine with a train, even when the rails are perfectly dry; if they are at all wet, a locomotive alone will hardly climb the ascent. Now upon the Mount Cenis road there are frequent ascents of one in twenty, and sometimes those of one in twelve.

Until within half a dozen years no one seemed to imagine that such ascents could be conquered. But about ten years ago Mr. Fell, an English engineer, conceived a plan for accomplishing this, and in 1865 obtained a temporary grant from the French and Italian governments for laying down and working a railway upon the line of Napoleon's Mount Cenis carriage road. Now that the thing has been accomplished, it all seems simple enough, and the wonder is that no one should have thought of it before.* All depends upon an additional centre rail, laid between the two rails on an ordinary track. This rail is the usual one; but it is laid down flatwise, so that the two running faces are presented upon either side. This centre rail, for reasons which will be apparent, is raised about a foot above the others.

* The general Idea was set forth forty years ago by Vignolles, a French engineer, and our own Ericsson; but we- believe it was first put into execution by Mr. Fell on the Mount Cenis Railway.

The locomotive, besides having the ordinary perpendicular driving-wheels, is furnished with two pairs of horizontal ones, which can, by means of a screw and lever, be made to grip the centre rail like a vice, with any required amount of force. The actual tractive force of the locomotive is thus more than doubled. Indeed, by multiplying these wheels, and increasing the force of their grip upon the central rail, it would be theoretically possible to construct a locomotive which should draw itself up an absolutely perpendicular ascent. The limitations of this theoretical power are only the limits of the tenacity in the metals of which the whole is composed.

There is also, in addition to the ordinary brake acting upon the wheels of the carriages, another which acts upon the centre rail. The form of this is shown in the accompanying cut. The flat face A, and the corresponding one on the opposite side, usually run smoothly close to the faces of the rail; but by turning the shaft B by means of a lever, connected with a handle upon the platform, the two sides are brought together like the jaws of a vice gripping the rail on either side. This centre brake alone will bring a train to a full stop within seventy yards. Combined with the ordinary wheel-brake, it will bring a train to a pause within less space than one needs to stop a carriage with the horses at a fair speed. This centre brake really controls the movement of the trains. The actual wear and tear upon it shows the work it has to do. As we found in the journey which we are to describe, it wears away so that its faces must be renewed at each trip. One other provision for safety is made upon this road. For each carriage is provided a deeply-flanged pair of guide-wheels, one running upon each side of the centre rail. These must prevent the train from breaking off the rails, even in rounding the sharpest curves. It is held tight upon the track at so many points that it must go on the rails.

Looking back upon all which was found evinced by a trip over the Fell Railroad, it seems to us that safety is secured upon a route whereof we have not the like for probable danger. We can not learn that any accident has ever happened on this route. We think, moreover, that the principle involved in the Fell Railroad is worthy of earnest consideration by our railway engineers. It seems to us that a railway constructed upon these principles can obviate not a few of the great difficulties which our engineers have to meet. For example, it seems to its that, had we studied it a few years ago, we should have never undertaken the construction of the Hoosac Tunnel. At all events, it is certain that herein is to be found means of reaching many of our mining regions hitherto supposed inaccessible to railways. We can by it mount ascents, and round curves steeper and sharper than any with which we have as yet fairly grappled.

So much by way of preliminary to what we shall have to say respecting the existing railway over the summit of the Mount Cenis Pass. Now for the tunnel through the ridge. Rising near Mount Cenis are two little rivers running in parallel but exactly opposite directions, upon either side of the ridge. The Arc, upon the French side, running northward, falls into the Isere, and thence into the Rhone, emptying into the Mediterranean near Marseilles. The Dora, upon the Italian side, running southward, falls into the Po, near Turin, and thence finds its way into the Adriatic. Now at one point, a score of miles from their source, these two rivers approach each other—the Are bending a little to the south, the Dora to the north. The distance at this point of approach is about eight miles; the elevation of the valley of the Are being here about 3700 feet; that of the Dora some 400 feet more, or 3000 below the summit of the pass. But between these two points the ridge of the Alps stands sentinel and barrier. This rocky barrier is pierced by the tunnel, 13,577 yards, about seven and seven-tenth miles; so that in that distance an ascent and descent of about 3000 feet are saved.

Having mastered all these details, we set out on our special tour of examination; the time being eighteen months ago, when no war raged in France. Leaving Paris, and traversing the fertile plains of Burgundy, passing Dijon and Macon, we climb the gentle lower slopes of the mountains, and reach the little village of San Michel, where the ascent of the Alps fairly begins. Here is the French terminus of the Fell Railway.

The carriages which are to convey us have a familiar look. They are almost exact counterparts of those of our city railways, just about as broad, the seats running lengthways along the sides. By special favor we are allowed to ride on the locomotive, and thus gain a better view than could be had from the carriage windows. In a few minutes we get our first view of the difficulties we have to surmount. The track rung straight up a hill steeper than any railway line we have ever seen, except the old incline—long since abandoned—at Schenectady, in New York, or the coal road at Mount Pisgah, in Pennsylvania. The actual ascent, by measurement, for half a mile, is one foot in eighteen; but if our eyes can be trusted it is not much less than the half of a right angle. But there is nothing in which our senses more deceive us than the real slope of a mountain-side. Thus, the Peak of Teneriffe, which to the eye is a perfect sugar-loaf, has an inclination of only 12 degrees, or one in thirty; and the very steepest face of Mont Blanc, which looks almost perpendicular, is less than 45 degrees, or one in eight, an inclination only half greater than some which we shall have to mount on this railway. The centre rail driving-wheels are screwed up, and the little engine pulls us up this rise with scarcely an apparent check. Then follows a comparatively slight ascent for ten miles, the, average rise being only one in forty-eight. This brings us to Modane Station. Here, looking across the gorge, we see a thin line of smoke rising far up the side of a steep mountain. This, we are told, marks the northern terminus of the tunnel, which we shall visit in a day or two. In the mean while we must go on to Turin, in order to obtain a permit to go into the tunnel; for of late it has been found necessary to exclude visitors, excepting for two days in the month, neither of which suits our time; and, moreover, we wish to examine matters more carefully than we could as part of a crowd on a regular open day.

Here also, looking southward, we get a glimpse of the ridge through, or rather under, which the tunnel is to pass. Following with our eye the line pointed out to us is, the direction of the tunnel, our vision is barred by a peak which, we are told, is called the "Grand Vallon," just midway between the two extremities of the tunnel—Fourneaux, where we see the smoke rising, and Bardonnêche, the opposite terminus on the Italian side. The Grand Vallon, we are told, rises to an altitude of 11,000 feet, only 454 less than that of Mount Cenis; and right under the highest point runs the tunnel; so that, measured in a straight line downward, fully a mile and a half of Alpine rock, at its highest point, overlies the tunnel. By rights the tunnel should be named the "Grand Vallon," for Mount Cenis is fully a score of miles from the nearest point of the tunnel. However, we suppose that the name—like that of 'America" for the New World, which should have been named "Columbia"—is too firmly fixed to be changed.

At Modane our train makes a brief halt to take in water for the engine, and to see that every thing is in order. Well it may, for right before us is an ascent steeper than any thing we have yet seen. It is, by actual measurement, one foot in twelve. So steep does it look that we can hardly believe that any train can overcome it. But we go at it with a dash, with the utmost speed which our little locomotive can accomplish. The screws are put on the horizontal driving-wheels, and up we go, our speed diminishing yard by yard, until it is reduced to four miles an hour. We could fairly out-walk the train. Should any thing give way, we must go back to Modane and try again; for, although the entire brake power would be sufficient to hold us fast on the incline, and prevent us from running back, the train could not be started again if the brakes were on; and if they were off, we should just slide down in spite of all the engine could do.

But no accident happens, as we believe none has hitherto happened here; and we breathe freer as we begin to ascend a gentler inclination. All the way we have been winding upward along the steep face of the cliff, upon the outer edge of Napoleon's road, of which our railway track occupies the outer edge, so that, without any parapet between us and the abyss below, we can look sheer, down precipices whose depths seem to us immeasurable. At Termignon the valley makes a sharp turn to the east, so that we can look back over the zigzag line by which we have so far ascended. Then comes a great bend back and forth, and another sharp ascent, by which in a mile we rise 350 feet.

This brings us to Lans-le-bourg, twenty-five miles from San Michel, and 2220 feet above that place. Here begins the great dead-lift of the road, for there is a further ascent of 2240 feet, which must be accomplished in a space of six miles. Here the engines are changed, for it is not safe to trust the work to one which has just been employed in dragging the train from San Michel. From our station on the locomotive we can mark the zigzags and curves of the road, which winds around like a huge snake. So sharp are the curves that our train of five carriages is often bent like a horse-shoe, the locomotive and the hinder car running in exactly opposite directions. Nothing but the centre rail and its appurtenances could prevent us from running off the track, and plunging sheer down the precipice which we overlook. At every moment something reminds us of the possible perils of the way. At intervals of only a quarter of a mile, perched upon some commanding point, are houses of refuge—solid little stone structures designed as shelters for travelers in the old diligence days (not very old either, for our railway dates back only five years) who should chance to be caught in a sudden snow-storm.

Ever and anon we plunge into darkness, for at the most exposed points the railway forms a covered way, having heavy plank walls, and a roof of corrugated iron. Two miles out of the six occupied by the ascent, and as many more upon the opposite descent, are thus roofed over.

But the summit is at length gained; then comes a run of five miles of almost level ground, when we begin the tremendous descent upon the Italian side. The descent is even more wonderful than the ascent, for it is almost continuous, with hardly an intervening level stretch. The views which we get are wonderful, changing every instant. At one moment we look far down over the lovely valley, dotted over with villages, vineyards, and farms. Then we turn a curve, and there is before us only a frowning wall of ragged rock. Again we seem to be literally banging midway between valley below and peak above. We actually slide down a great part of the descent of almost twenty miles from the summit to Susa, the Italian terminus of the Fell Railway. Here, even more clearly than on the ascent, the value of the centre rail was shown. The wheel-brakes were not once applied, the centre brake alone regulating the speed.

The illustrations which we give, selected from an immense number, show better than can be done by words some of the most striking features of the scenery upon the route. At the head of the article is the Echelle du Diable "Devil's Ladder"—a little way down the Italian slope. This "ladder" is a zigzag, rising tier over tier, constructed to take the place of a portion of the road as originally laid out by Napoleon's engineers, but which was abandoned on account of the avalanches which come down. At the very foot of the ladder are seen the remains of one or two vehicles which have broken down; and midway up is seen a diligence, drawn by twelve horses, toiling up the ascent, while another is shown mounted upon runners. The railway does not climb the ladder, but leaves it for the old road of Napoleon, and is protected by a long line of covered galleries. Fort Essillon is near Modane. Here the road passes high above the river Arc, whose gorge forms a natural fosse, surmounted by a fortress, now dismantled, built by the Sardinians to guard the pass. This fort is on the side of the gorge opposite the road, with which it is connected by a light iron bridge, called the "Devil's Bridge." It looks like a slender thread stretching across the chasm. On the right side is seen the railroad train toiling up, one of the steepest ascents. Here is one of the most striking views on the route. The remaining illustrations tell their own story.

In six hours after leaving San Michel we reach the foot of the mountain on the opposite side of the Alps, where the Fell Railway terminates, at the little town of Susa, at the head of the broad valley of the Po. Thence a ride of thirty miles, accomplished in an hour, brings us to the gay, bustling city of Turin. Here, repairing to the office of the "Direzione Tecnica del Traforo delle Alpi," we present our credentials and receive a permit to visit the tunnel on an off day; and also a special letter to Signor Genesio, the local superintendent, which will secure to us every facility for a thorough examination of the work.

The Italian terminus of the tunnel is less readily accessible than the French one; so we retrace our way to Modane, and walk over and up to Fourneaux, a little village dug in, as it were, upon the steep hill-side. A more unpleasant place, filled with less pleasing people, it would be hard to find. We never before saw so many people afflicted with that ugly, wen-like excrescence, the goitre, and its accompaniment, apparent idiocy. But the scenery is magnificent. Above us rises the Grand Vallon, its upper portion white with snow; while, lower down, the cliffs are clothed with firs and pines, looking, in contrast with the snow, almost black. Lower still are trees and shrubs, whose foliage, clad in bright autumnal hues, reminds us of what we have seen among our own White Mountains of New Hampshire. But far higher above—almost twice higher than Mount Washington—are piled the Alpine peaks, soaring one above another, and shutting, in the vision at either extremity of the valley.

Here let us gather up what, during a three days' stay, we learn, by the abundant courtesy of the officials, of the origin and mode of construction of the tunnel which we are to explore.

The idea of the tunnel appears to have been first broached, about 1832, by M. Medail, a Piedmontese, born at Bardonnêche, who pointed out where lay the least thickness of the Alps between Piedmont and Savoy. Ten years later he presented to the Italian government a plan for a tunnel through the ridge. Two engineers, MM. Maus and Sismonda, were thereupon appointed to investigate the matter. After four years they reported favorably upon the line which has been adopted. The great difficulty lay not in the fact that it must run so far beneath the summit of the mountain; since, for all practical purposes, it made no difference whether this towered half a mile or five miles above. Either distance would equally prevent perpendicular shafts from being sunk to the level of the line, so that the working could be carried on simultaneously at many points. The mountain could be attacked only at its opposite sides, from which the two ends of the tunnel, well-nigh eight miles apart, must be driven toward each other. Moreover, how were the hundreds of laborers to be supplied with air, which could only reach them for almost four miles underground? Again, as far as was then known, only human labor could be employed. Steam-power was out of the question; for the steam-engine must have fire, and fire must have abundant air, as well as coal and water. It now seems strange to us that, with the knowledge then existing, the work should ever have been seriously considered. Looking back upon the work done, we may safely say that, by no means known to man in 1855, could the excavation of this tunnel have been performed in half a century. Only so many men at a time could work within the contracted space. Unless some mechanical means of drilling other than that of steam-power should be devised, the work, if undertaken, must have been abandoned before it had been a quarter completed.

But, as it happened, about 1850, three young Italian engineers—Sommellier, Grandis, and Grattoni—were engaged in a series of investigations. They had no thought of the Mount Cenis Tunnel, with which, however, their names have come to be inseparably connected. All that they then thought of was a means of propelling, by means of compressed air, railway trains up a steep incline among the Apennines. The idea was to use compressed air as the motive power. The principle upon which they started was one already well established—that air, when compressed, has a great expansive and elastic power. This principle is well shown in the toy known as the "air-gun." The amount of possible force thus to be acquired had long been settled. Air compressed to one-sixth of its natural state has an expansive force of about 84 pounds to the square inch. This is about half more than the pressure of steam in an ordinary stationary engine, as usually worked.* The merest tyro in mechanics need not be told that no machinery creates power. Levers and pulleys and cogs simply enable us to concentrate or apply power already created at the point where we wish to use it; and this transfer is always accompanied by more or less loss. But, as it happened, there was, just where Sommellier and his associates wished to use this compressed air, a river, which gave abundant force for compressing the air. The problem now became a purely mechanical one. It was merely to transfer the water-power of the river into the shape of condensed air. As we shall see, the same advantage was to be found at each extremity of the proposed Alpine tunnel.

* We find that the engine which moves the entire mass of machinery in the establishment where this Magazine is printed is usually worked at a pressure of from 50 to 60 pounds. It is safe, however, to increase this by a half.

About 1855 Mr. Bartlett, an English engineer, invented an apparatus by means of which a drill, driven by steam, was made to perforate a wall of rock to far greater advantage than the same work could be done by hand. His idea was mainly the use of his machine in coal mining in England, where, we believe, it has been and is used to advantage. But, as we have seen, Bartlett's steam-drill could not be used in the Alpine tunnel; while the Italian air-engine was equally unavailable in an English mine, where no water-power for compressing the air was to be had.

It occurred to Sommellier and his associates that the two inventions might be combined into one, and used to bore through the Alps. The result of this is shown in what we shall have to see, and explain as best we may.

Sommellier and his friends proposed their plan to the Italian government of their day. How the putting this into execution was postponed for years, until the troubles connected with the rise of the new kingdom of Italy got, in a fashion, settled, is a story too long to be told here. Suffice it to say that finally, under the administration of Cavour, somewhere about 1857, the Italian government fairly took upon itself the work of digging the Mount Cenis Tunnel.

The first thing was to fix mathematically upon the exact direction which the tunnel should take, so that the two opposite headings should meet under the summit of the Great Vallon. In engineering phrase, the horizontal axis of the tunnel was to be fixed; that is, a line was to be marked out over the crests right under which, no matter how far below, the tunnel should run. In fixing this line the two engineers, Copello and Borelli, to whom the work was confided, encountered great difficulties. They had to scale the rocky sides of cliffs, making paths over untrodden regions, and use their surveying instruments in a region where, at any moment, a sudden storm might interrupt their work. But it was at length performed, and from the summit of the Great Vallon, 11,000 feet above the sea, down the slope on either side, a line was marked out, right under which the tunnel should run. That the tunnel should nowhere deviate a foot to the right or the left from following this line, lay fairly within the known limits of engineering skill. The compass, carefully used, would settle that. But there was a far more serious difficulty to be met. The two portions of the tunnel must not only approach each other in the same direction, east and west, but they should meet at the same vertical elevation. The precise inclination of the two excavations must be rectified at every rod; otherwise, when they should have met at the centre, one might have been yards or rods above or below, the other. There were not wanting those who, up to the very last moment, doubted whether the two workings would ever meet. But the final result, known first on Christmas-day, 1870, showed how accurately all had, been done. When the last foot of rock had been broken through, the two excavations struck each other almost to an inch. The first man who passed through the dividing rock, we are told, was Grattoni, one of the three of whom we have spoken. If we could have chosen the proudest three single moments which could mark a human life, one should have been that when Napoleon, at Austerlitz, saw the Austrian line fairly cut in two; another should have been Wellington's, when he saw Napoleon's Imperial Guard tumbling back in rout from its charge upon his solid square; the third should have been that of Grattoni, when, first of all men, he passed through the Alpine tunnel.

At Fourneaux we examine the apparatus for furnishing the compressed air which is to supply the perforating engine, which we are soon to see at work. What we see is rather simple. Close down at the edge of the Arc is a waterwheel, always at work. On the bank above is a huge tank, upheld by a score or so of iron columns. It looks like an ordinary gas-holder. Running up to this are a number of hollow tubes, each opening into the tank by a valve, opening up into the tank, so that every thing going up can pass, but nothing can come back. The wheel drives the water up the tube, forcing the air before it into the tank. When the column of water has reached the top of the tube a valve at the bottom is closed, cutting off the water, while another is opened, allowing that which has entered to pass off; while at the same time another valve at the top is opened, admitting air into the pipe. Then, when the pipe has been emptied of water, the escape-valve is closed and the supply-valve opened, and the rising water again drives the air before it into the tank; and soon perpetually. All this operation, so hard to describe, is easy to understand when once seen. The, current of the river turns the, wheel; the wheel forces up water into the pipe; this condenses the air contained in the pipe; and so a force which costs nothing, and which, for untold ages has lain useless, is made, under human guidance, to work miles away. At Bardonnêche, the other end of the tunnel, they are able to dispense with the water-wheel and the whole pumping apparatus. There, high up on the mountainside, is a stream which never fails. From this the water is conveyed by pipes into the condensing cylinders, rising when the supply-valve is opened, and falling when it is closed. Otherwise all is the same as we see at Fourneaux.

The condensing apparatus at Fourneaux is about half a mile from the mouth of the tunnel. The condensed air is borne from the tank through an iron pipe of eight inches in diameter. As we pass up to the mouth of the tunnel we see this pipe running along the way. We notice the manner in which it is laid, and are inclined to think it absurd. At intervals of three or four yards are low pillars of masonry, upon the top of which is a short piece of pipe, mounted upon rollers. The intervening pieces are braced firmly by iron rods let into the upholding masonry.

"What is the use of this?" we ask of our guide.

"The temperature of the valley outside of the tunnel," he replies, "often varies fifty degrees in the course of a single day. Now, if our pipe were here laid in the usual way, its expansion and contraction under these quick changes of temperature would soon tear it to pieces. We have to make it practically an elastic tube. Now see how our plan works. The ends of the fixed parts, between the pillars, fit into those upon the tops of the pillars, much as one slide of a telescope runs into another. Now when our tube expands by heat, the fixed, part is driven a little into the movable part, resting on the pillars; when the tube contracts by cold it is pulled a little out. So our pipe is always of the same length, no matter what may be the expansion or contraction of its several parts. The parts resting upon rollers are made, so simply to give free play to the whole. The joints—there are hundreds of them—are made as nearly air-tight as possible by means of rubber or leather padding. So nearly air-tight are they, that the, escape of air by all is hardly appreciable. One part in sixty is all that is lost in the whole three miles and more between the reservoir and the place where we are now working. Fairly inside the tunnel, where the temperature is equable, the pipes are laid in the usual way. Don't you see?"

We did see, and inwardly resolved that we would not thereafter take it upon ourselves to pass summary judgment upon any engineering question which Would come before us in the tunnel. It might be that the engineers were wiser than we.

The mouth of the tunnel, which we reach after a walk of half a mile, presents nothing specially notable. It is a mere hole in a hillside, only it looked a little larger than any one which we had seen—say the Bergen Tunnel, near New York. It is a simple horseshoe arch, whereof the height is within a few inches of twenty-five feet, and the greatest breadth a foot or two more. Wagons, loaded with all sorts of materials, are going in; others, equally laden, are coming out. Fairly within, it is the, most dark, damp, and disagreeable place we ever entered, even where the work is pronounced finished. There is, indeed, a solid floor over which to walk; a solid wall of smooth masonry incloses us on both sides. The stones of which it is constructed, we are told, have been brought from miles away, for hereabouts there is no rock which the workmen could hew into shape for such, purpose. Each step the way grows darker. We look back toward the entrance through which we have come. It grows smaller and smaller, until at last it is lost to view. Then before, behind, above, and around is utter darkness, broken only by the candles which we carry, and a faint gleam from some gas-light shining like a star in the distance.

Meanwhile our guide was profuse in his explanations. I I The floor," be said, "looks level; but right in the centre is a covered way, three or four feet high and broad., It was at first designed merely as a conduit for water-pipes and the like. But one day—it was in 1863—when we were working through a rather soft bit of rock, a great fall of rubbish came down, blocking up the tunnel, and shutting in three-score men who were working beyond. They gave themselves up for lost, until one, who had his wits about him, bethought himself of this covered way of escape, through which all crawled out. Since then nobody is afraid of being shut up here."

As we proceed still onward the air grows hotter. A thermometer banging by the wall, which we read by the light of our candle, indicates a temperature of 800. "Where are we now?" we ask. "About two miles from the mouth, nearly at the end of the finished part on our side, and close upon that in course of excavation, where you can see how the work is done."

Hardly were the words spoken before a gust of smoke dashed full in our faces.

"They have been letting off a blast; we shall be just in time to see the work going on."

Hitherto we had been walking along what might have been some deserted city street. All at once the way narrowed at the sides and sank down overhead. "Here we are," said our guide, "at the entrance of the gallery in corso di scavazione; for we don't bore this big hole through at once. We make it in three drifts, two side by side, and one at the top; one a bit ahead of the other. The Italians drive the top drift ahead; we put in one of our side ones first."

All this was said in such an odd mixture of languages that we are to this day in doubt as to the nationality of our guide. If he was English, he had learned little Italian; if he was Italian, he had learned little English. Could he have been a Yankee who had strayed from the Alleghanies to the Alps? Once or twice we thought his speech bewrayed him. But be he who he might, he evidently understood engineering. We shall hereafter translate his lingua Italiana into English.

"Why is this?" we ask. "One way of making the drifts must be better than the other. Why not find out the best way, and follow it on both sides?"

"It is all plain enough when once you come to understand it. The Italian month of the tunnel at Bardonnêche had to be a little more than a hundred feet above ours at Fourneaux; and even then we had to make our mouth almost four hundred feet higher than we would have liked to do. You would suppose that the line should have run straight down from one end to the other. That would have answered very well for as, but not for our friends on the opposite side; for, before they had run down half a mile, they would have been flooded. Water in one way or another is always coming into the tunnel; and water, you know, won't run up hill. So, instead of coming down to us, they were obliged to go up a little, to jet their water run off on their own side. To make this ascent as slight as possible, they first excavated from the top. When our ends meet at the bottom the water may ran which way it pleases. Do you see?"

We saw again, and were still further inwardly assured that we had yet something to learn in the matter of engineering.

No sooner had we entered the narrow advanced gallery than we seemed to come into a new world. The temperature was certainly high, but the air was pure and sweet, acting like balm upon our lungs, which had been laboring in the sulphurous smoke. This, as we soon learned was owing to the fresh air which, after having done its work in the "Affusto," which we were to see, had to find its way out, driving before it all foul exhalations toward the mouth of the tunnel.

"Here we are," said our guide, "just about under the highest point of the Grand Vallon. I suppose there is a mile and a half of solid rock right over our heads. We are three miles into the mountain. They are a little further on the other side; for we met some harder rock than they did, which made us go slower. And this," he continued, patting a piece of machinery, "is our affusto, or, as the French call it, affût, which in English means just 'carriage.' The nine things which you see pecking away at the hard rock in front are the perforators; or, as we call them in French, perforatrices—'Mademoiselle Borers.' This is what has done the work of boring into the Alps."

Instructed as to what the affusto has done, we look upon it with a kind of reverence; though what we see, as shown in our illustration, is nowise remarkable. Take an ordinary locomotive engine, remove the furnace and boiler, and you have a fair idea of it. There are pipes, wheels, and handles in bewildering confusion, and a score of men, who seem to know what they are about, in all sorts of attitudes, managing the whole. The one thing which strikes us as new is the nine rods, looking like the long antenna of a beetle, from each of which something comes out and in right against the face of the rock.

"Count the strokes from one of these," said our guide. Watch in hand, as though we were timing a racer, we count. In a minute there are just two hundred strokes.

"Each blow," said our guide, "has a force of two hundred pounds, quite as heavy as are given by a miner with a sledge-hammer. Did you ever count how many blows a miner will give in a minute?"

We had seen mining operations enough, but had never thought of counting the number of blows. We went through the operation with our cane, as nearly as we could, and found that we made about twenty strokes in a minute.

"That's about fair," said our guide. "A miner, with an assistant to handle the drill, will give about twenty hammer strokes in a minute; but not more than five pairs of workmen could find room to work here at once. They would give all at once a hundred blows a minute. Now Madame Affût, with her nine daughters, the Perforatrices, gives eighteen hundred, quite as heavy, in the same time. To be sure, the madame and her daughters want about a score of men to wait upon them. But she and they manage to strike eighteen hundred blows a minute, while it would take one hundred and eighty men, with hammer and drill, to do the same labor, even could they have found space in which to work, which they couldn't. Don't you see?"

Again we saw, and were abashed.

"Look again," said our guide, with professional enthusiasm, "and you will see how it all works. Our motive power, as you know, comes from the water-wheel at Fourneaux, which condenses the air. Thence it comes up where we are. We have got our power where we want it, in the affusto. We use it just as though it were steam. See that cylinder; in it works a piston, to the end of which is attached a drill. Now, when the air is let on, it drives the drill against the rock; and when the air is cut off, back comes the drill. Look again, and you will see that at each stroke the drill turns around a little. To make this rotatory movement takes more than half of the machinery which you see; but it must be done. In handwork one man turns the drill, while the other gives the blow. Affusto does both; she strikes the blow and turns the drill. Again, iron striking stone educes fire. We must put this out as fast as it occurs. So you see that with each perforatrice is a man, holding what looks like a common garden hose, through which he throws water into the hole made by the drill. You see that each perforatrice works independently of all the rest, so that any change in the movement of one does not affect the others. Moreover, which you will hardly notice, each has a flexible joint, so that the drill may be directed up or down, to the right or the left, as may be required. Ah, there you see; that drill near the middle has gone deep enough, and they are going to have it make a new hole."

The drill to which our attention was called was withdrawn, and put at a point a yard distant. For a minute or two it seemed to strike "wildly," as pugilists say, as if not knowing just where it meant to hit. A man with a booked rod guided it for a little. But as soon as a hole a few inches deep was made, the drill worked of itself.

"How deep do you drill?" we asked.

"That depends upon the character of the rock. In this, through which we are now passing, about a yard. In the hard quartz which we met a while ago, when they got a start of us on the other side, we went only half as deep; and that was fearfully hard upon the drills. In ten minutes they got so blunted that we had to change them. As it is, we wear out about a hundred and fifty drills and two perforators for every yard we gain. M. Sommelier estimates that, all told, we shall use up a couple of thousand of the Mademoiselles Perforatrices before we get through. If we get off with the loss of that number, it will be less than I expect. The general idea is to drill about eight hours at a time, and then blast. To clear away the stone takes about half as long as it does to do the drilling; so that generally we blast twice a day. A day with us means four-and-twenty hours; for the work never stops. We work in gangs, eight hours on and sixteen hours off. Eight working hours out of the twenty-four, I dare say, seems short time to you; but it has been found to be as much as men can well do in this atmosphere. We know only two holidays Christmas and Easter-Sunday."

We had been advised to wait for a blast, the crowning event of each eight hours' work. But the continuous "thuds" of the nine perforators—thirty to a second, could we have counted them—grew monotonous. So we strayed down the tunnel to see how the work was being done. What we saw was just this: where the two or three drifts had been blasted into one, numbers of half-naked men were working away to clear off the rubbish and make all smooth.

Our guide did not seem to care much about these investigations. For a while he left us quite to ourselves. Possibly he had found some friends in the tunnel. At all events, when we got back to the head of the gallery he was in great good humor, and altogether fluent in explanation.

"You are just in time," he said, "to see the work done. Look at the drillings."

We, looked: and what we saw, and the explanation thereof, are shown in the two following diagrams. The wall before us—eight feet and a few inches high, and a little broader—was honey-combed with holes, about fifty in all, apparently placed at random. The face of a sand-hill inhabited by bank swallows presents an exact representation of its appearance. But, as we found, and have shown on the diagrams, these drillings are by no means made at random.

The affusto, having, through a flexible pipe, given a strong blast of wind into each hole, driving out all the dust, was wheeled back, and we saw workmen putting up a heavy barricade of thick oaken plank behind us. Others began putting in the charges of powder. We noticed that they charged half a dozen or so near the centre, then stopped; and all went back behind the barricade. We prudently went with them.

"Why do you not charge all the holes, and fire them off at once?" we ask.

"Wait a moment, and you will see," we are told.

At the moment the sound of the explosion was heard, and as soon as the smoke had somewhat cleared away we reentered. There was a ragged hole a yard deep, and perhaps eighteen inches in diameter, in the centre of the rocky face.

"You see the rock gives way at the point of least resistance, and that was where six or eight holes had been bored close together. Now we shall charge another and larger circuit of holes. The rock will, of course, again give way toward the weakest point—that is, toward this hole which we have already made, enlarging it to a couple of yards. Then we shall charge the remaining holes, and all the rock will still be blown inward, leaving a tolerably even surface all around the space marked out by the perforators."

The working of these blasts is shown in the two diagrams. The position of the first hole is represented in the cross section. Its general shape is indicated by the heavy dotted lines in the longitudinal section. The outline of the entire excavation is represented by light broken lines. We could not fail to perceive the economy in power secured by blasting successively, instead of all at once; and again resolved that we would not undertake to instruct the Mount Cenis engineers how to do their work. Indeed, we rather wished that, when the tunnel shall be completed, some of them would come to us across the Atlantic. We think they could teach us something.

Afterward, when we considered that it was the River Arc which had really—though indirectly, through Sommellier's air-pipe—dug through almost four miles of solid Alpine rock, miles from and hundreds, of feet above its bed—and when we called to mind the superabundance of water-power which we have lost hitherto, because lying in ravines so deep as to be practically inaccessible—and when we considered how that wasted water-power might be translated into compressed air, and so carried far away to places where it could be utilized-we became convinced that herein, as well as in the Yell Railway, lay matter worthy of profound consideration. What form our speculations finally assumed we have not space here to put down.

We had in six hours seen the entire working of the operations on the Mount Cenis Tunnel; for the rock blasted out having been hauled away, the affusto was wheeled back, and again began its work as before.

It must not be supposed that the work was completed last Christmas-day. The heads of the advance drifts then met. The tunnel had yet to be blasted to its full extent; and, moreover, thirty-four miles of most difficult railway were to be constructed to connect the tunnel with the French and Italian lines, between which it forms a link. We have in this paper simply shown what the Mount Cenis Tunnel really is, giving attention particularly, to the difficulties involved in its construction. Possibly, before this meets the eyes of our readers the tunnel will have been opened.

A few facts and figures, by way of memoranda and suggestion, and we have done: the actual work upon the tunnel was begun in 1859; the air-perforators, without which the whole must have been a failure, were introduced in 1861. In 1863, Savoy having been annexed to France, an agreement was made between the French and Italian governments, in accordance with which Italy was to execute the whole within ten years, receiving from France about 32,000,000 francs as payment for half of the work, with deductions in case the completion should be delayed. It is generally understood that the French payment will fall short of half the total cost, which is estimated now at 75,000,000 francs, say $15,000,000. But it should also be borne in mind that this sum means touch more in Italy than with us. Thus, the payment of ordinary laborers on the tunnel is three francs a day; with us the same men would command about two dollars. It is fair to estimate that, measured by our standard, the cost of the tunnel itself, less than eight miles long, will be $50,000,000. But this is only a part of the actual working cost. As we have said, thirty-four miles of railroad have to be built, and the whole equipped with engines and carriages. We have before us two estimates of the probable entire cost, which readers may take for what they are worth, only bearing in mind that engineers' estimates are usually far short of actual cost. Captain Tyler, the English Board of Trade inspector, in 1868, estimated the entire cost at £5,400,000($27,000,000). Sir Cusack Roney, an eminent British contractor, estimates it at £7,200,000 ($36,000,000). Both sums are based upon the price of Italian labor. We should, in counting the cost, multiply by something more than three, and so judge that, taking a fair mean between the two estimates, the whole cost of the Mount Cenis Tunnel and Railway, 42 miles in all, will not fall short of $100,000,000. That, as a commercial enterprise, it can ever pay, seems out of the question. And it may be safely assumed that, as it is the first, so it will be the last enterprise of the kind which will be undertaken for generations. But, as we have before intimated, two things, hardly more than incidental to the whole idea, are worth to the world much more than all has cost. These two things are: Fell's—or rather, perhaps, Ericsson's—centre rail and appurtenances, and Sommellier's air-condensing apparatus.

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