THE EIFFEL TOWER. 731 



sion as in compressiou, aud can be put together perfectly by rivetting — 

 tlie execution i^reseuted no insurmountable difficulties. Moreover, 

 met'il constructions can now be planned with such accuracy as to sanc- 

 tion 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 deter- 

 mined 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 intro- 

 duction. 



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 ibuutiation 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 })ounds and 55 pounds to the square 

 inch, surmounted by a layer of sand and gravel of varying depth, ad- 

 mirably calculiited 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 nrea of GO 

 square meters. In tlie 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 — suffi- 

 ciently assured by its own weight — gives nevertheless additional secu- 

 rity, and has moreover been useful in the construction of the iron- 

 work. 



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, wo 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 ]>ier can be dis- 

 placed and raised as much as is necessary by inserting steel wedges 

 beneath it. 



The raising into place of the iron-work which foi-ms the upper part 

 of the tower was accomplished by derricks and windlasses. As soon 

 as the piers reached a height of 100 feet their inclination rendered 



