THE EIFFEL TOWER.*

By G. EIFFEL.

The notion of a tower 1,000 feet in height is not new. It has haunted the imagination of Englishmen and Americans. As early as 1833, the celebrated English engineer Trevitick proposed to construct a cast-iron tower 1,000 feet high, of which the diameter should be 100 feet at the base and 4 feet at the summit. But his project was never put in execution, and was but imperfectly worked out even on paper.

At the time of the Exhibition in Philadelphia, in 1876, the great American engineers, Messrs. Clarke and Reeves, brought forward a new project. Their tower was to consist of an iron cylinder 9 meters in diameter as a nucleus, and supported by a series of metal buttresses disposed round it and starting from a base with a diameter of 45 ineters. This was a distinct improvement on the English project, although it still left room for criticism; and yet the Americans, in spite of their enterprising spirit and the national enthusiasm excited by this conception, shrank from its execution.

In 1881, M. Sébillot proposed to light Paris by an electric lamp placed at a height of 1,000 feet. This idea, which has, in my opinion, no practical value, had no better fate than its predecessors. I need only mention the designs, some in masonry, some in metal work and masonry combined, others, lastly, in wood, like the proposed tower for the Brussels Exhibition, which were produced at the same time as my But all these remained in the domain of fancy, proposals easy to frame but hard to execute. I come to the project which has been realized.

Own.

In 1885, after the studies which my engineers and I had occasion to make with regard to the lofty metal piers which support railway viaducts like that of Garabit, we were led to believe that it was possible to construct these without any great difficulty of a much greater height than any hitherto made which did not exceed 230 feet. We anned on these lines a great pier for a viaduct which should have a height of 395 feet and a base of 131 feet.

*From the New Review. Copied in the Eclectic Magazine, Sept., 1889, Vol. L., pp. 355-359.

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The result of these studies led me, with a view to the exhibition of 1889, to propose the erection of the tower, now completed, of which the first plans had been drawn out by two of my chief engineers, Messrs. Nouguier and Koechlin, and by M. Sauvestre, an architect.

The fundamental idea of these pylons or great archways is based on a method of construction peculiar to me, of which the principal consists in giving to the edges of the pyramid a curve of such a nature that this pyramid shall be capable of resisting the force of the wind, without necessitating the junction of the edges by diagonals, as is usually done.

On this principal the tower was designed in the form of a pyramid, with four curved supports, isolated from each other and joined only by the platforms of the different stories. Higher up only, and where the four supports are suffi ciently close to each other, the ordinary diagonals are used.

In June, 1886, a commission nominated by M. Lockroy, then minister of commerce and industry, finally accepted the plans I had submitted to it, and on January 8, 1887, the agreement with the State and the City of Paris was signed, fixing the conditions under which the tower was to be constructed.

It is needless to state that considerable energy and perseverance were required to attain this result, for there was much resistance to Lovercome, and my project had many opponents.

But I was sustained by the belief that what I proposed would contribute to the honor of our national industry and to the success of the exhibition, and it was not without a legitimate sense of satisfaction that I saw an army of navvies begin, on January 28, 1887, those excavations at the bottom of which were to rest the four feet of the tower which had never been out of my thoughts for the last two years.

I felt moreover-in spite of the violent attacks to which my project had been exposed-that public opinion was on my side, and that a crowd of unknown friends were ready to honor this bold enterprise as soon as it took form. The imagination of men was struck by the colossal dimensions of the edifice, especially in the matter of height.

The towers of Notre Dame de Paris reach a height of 217 feet; the Pantheon 260 feet; the dome of the Invalides, which is the highest monument in Paris, 344 feet; Strasburg Cathedral is 466 feet; the Great Pyramid of Egypt 479 feet; the Cathedral of Rouen rises 492 feet from the ground, and is only surpassed by Cologne Cathedral, which, lately completed, attains to 522 feet; but the Americans again outdid this by erecting at Washington an immense obelisk in masonry which reaches a height of 555 feet, and was constructed with immense difficulty.

Experience has shown however that masonry is not suitable for a construction of the kind. With iron, on the contrary,-of which the properties are so remarkable, since it may be as readily employed in ten

sion as in compression, and can be put together perfectly by rivettingthe execution preseated no insurmountable difficulties. Moreover, met il constructions can now be planned with such accuracy as to sanction the boldness which results from full knowledge.

Lastly, without any desire to flatter our national vanity, I may be allowed to say that French industry has held and still holds a high place in Europe in the art of building in iron.

Hence the material of which the tower was to be built was determined not only by the fact that it rendered construction possible, but also because it would supply a brilliant example of a modern industry in which France has been more especially distinguished since its introduction.

The base of the tower consists of four great piers, which bear the names of the four cardinal points. The first matter which offered itself for consideration was the question of the solidity of the foundation of these four piers. A series of borings showed that the subsoil in the Champ de Mars was composed of a deep stratum of clay capable of supporting a weight of between 45 pounds and 55 pounds to the square inch, surmounted by a layer of sand and graver of varying depth, admirably calculated to receive the foundations. The actual position of the tower was determined by considerations relative to the depth of this stratum, since it was impossible to rest the piers directly on the clay. The foundation of each pier is now separated from the clay by a sufficient thickness of gravel.

Each of the main supports of the tower rests on blocks of masonry, and the masonry rests on beds of concrete which cover an area of 60 square meters. In the center of each pile of stone-work, are two great iron bars 25 feet 6 inches in length and 4 inches in diameter, which, by means of iron cramps, unite almost all parts of the masonry. This anchorage, which is not necessary to the stability of the tower-sufficiently assured by its own weight-gives nevertheless additional security, and has moreover been useful in the construction of the ironwork.

It will be seen from the foregoing description that the foundations. are established under conditions of great security, and that in the choice of materials and in the dimensions ample margin has been allowed, so as to leave no room for doubt with regard to their solidity.

Nevertheless, to render perfectly certain that the feet of the tower should remain absolutely level in any event, we have made room, at the angles of the piers where they rest on the masonry, for hydraulic presses of 800 tons. By means of these presses each pier can be displaced and raised as much as is necessary by inserting steel wedges eneath it.

The raising into place of the iron-work which forms the upper part the tower was accomplished by derricks and windlasses. As soon he piers reached a height of 100 feet their inclination rendered

scaffolding necessary to carry on the construction to a height of 160 feet, at which point are established the horizontal beams

four piers and forming the skeleton of the first story. The s struction of the first platform was a great step toward the the work.

The raising of the pillars between the first and second platforms rapidly accomplished by the same method as that employ the ground and the first story, i. e., the pieces of iron were r four cranes attached to the beams of the lift placed in each | et.

The work went forward so rapidly that in July, 1888, the fur le were united by the beams of the second story, at a height on 582 ft and by the 14th of the month the second platform was fixed. fireworks were displayed at the Fête Nationale.

The erection of that part of the tower comprised between h rod platform and the summit was carried out by means of the sebe et. as had served for the lower part; but these no longer wo inclined plane, but were raised along an upright, formed by 1 guide of the higher lifts.

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The total weight of the ironwork in the tower is rather 7,000 tons, without counting that in the caissons, which forms of the foundations, or that in the machinery of the lifts.

The different parts of the tower are reached by staircase and d There are easy stairs in the east and west piers, which give the first story, and it is calculated that by using one for asce for descent they will allow more than two thousand persons and come down in the hour. From the first platform to th there are four winding staircases, one in each pier, and from 1 platform to the summit there is a single winding staircase, wu boy ever (unlike the others) is not intended for the use of visitor officials only.

On the first platform is a covered gallery, with arcades, wh» tors can enjoy a view of Paris and its environs, as well as of bition, with four refreshment rooms in the center,—Anglo- \a' Flemish, Russian, and French. On the second story is a se ered gallery; and in the center is the station where passenge 360 from the lifts which move on an inclined plane of the lower 1 tower, to the vertical lifts of the upper portion.

On the third story is a great saloon more than 50 feet squ

in by glass on all sides, and whence, sheltered from wind and the spectator can contemplate the magnificent panorama, 45 legn extent, which is displayed beneath him. Above this room a bora tories and observatories for scientific purposes, and in the cater the winding stair leading to the light-house whence the electric lig over the whole of Paris.

The lifts are on three different systems, and all are provale breaks, and otherwise insured against the possibility of serious

They are all worked by hydraulic power, and together are capable of conveying 2,350 persons in an hour to the first and second stories, and 750 to the summit, the whole ascent being effected in seven minutes. If we include the staircases it will be possible for 5,000 persons to visit the tower in the space of an hour.

The tower is now known to the whole world; it has struck the imagi nation of every nation, and inspired the most remote with the desire of visiting the Exhibition. The press of all countries confirms this statement, and I have myself received continual proofs of the universal curiosity and interest excited by the monument.

The visitors who go to the top of the tower have beneath their eyes a magnificent panorama. At their feet they see the great city, with its innumerable monuments, its avenues, its towers, and its domes; the Seine, which winds through it like a long ribbon of steel; farther off, the green circle of the hills which surround Paris; and beyond these, again, the wide horizon stretching 112 miles from north to south. At night the spectacle is no less beautiful. Paris with all its lights is like fairy-land, but in this aspect it has hitherto been known only to aeronauts, on whom its beauty has always made a strong impression. The construction of the tower will enable thousands to contemplate a spec tacle of new and incomparable loveliness..

Then too for scientific and defensive purposes the gigantic monument will be of great utility. A recent writer, M. Max de Nansouty, says:

"In case of war or seige the movements of the enemy might be observed from the tower within a radius of 50 miles, and that above the heights which encircle Paris, and on which are constructed our new fortifications. Had we possessed the tower at the time of the seige of Paris, in 1870, with the powerful electric lights with which it will be furnished, who knows if the chances of the strife would not have been profoundly modified? The tower would be a means of constant and easy communication between Paris and the provinces by the aid of optical telegraphy, which has in various forms attained such a remarkable degree of perfection."

The tower is itself at such a distance from the fortifications that it is absolutely out of reach of the enemy's battery

It will be moreover a wonderful meteorological observatory, whence the direction and the force of atmospheric currents can be usefully studied, from the point of view of science and hygiene, as well as the condition and the chemical composition of the atmosphere, the amount of electricity and moisture it contains, the variations of temperature at different heights, atmospherical polarization, etc. It is specially adapted for an astronomical observatory; for the purity of the air at this great height above the low-lying mists, which so often cloud the horizon of Paris, will allow of a number of observations often impossible in ur climate.