736 THE EIFFEL TOWER. 



THE EIFFEL TOWEE.* 



By William A. Eddy. 



A tower about 1,000 feet in height was first thought of during the 

 organization of the (Centennial Exposition at Philadelphia, in 1870, and 

 its possible construction was discussed in the newspapers at the time. 

 But consultation with engineers and architects probably resulted in 

 the conviction that the scheme was impracticable, and the expense be 

 yond the value of the investment, especially if masonry were used. 

 Aside from the question of outlay, a serious difliculty in the construc- 

 tion of any kind of material to such an altitude, there are questions of 

 pressure and danger that daunt experienced engineers. M. G. Eiffel, 

 constructor of some of the greatest works in France, notably the trestle- 

 work viaduct at Garabit, 407 feet high, concluded that the building of 

 such a tower had not been attempted in ancient times, so far as known, 

 because iron construction then lacked the lightness, strength, and adapt- 

 ability seen in modern work. The enormous weight of masonry in so 

 great a mass would not only imperil, by its tremendous pressure, the 

 courses of stone near the ground, but would cause an irregular settling 

 of the foundations, as in the well-known instance of the Leaning Toyer 

 of Pisa. In modern work, a pressure of 06 pounds for each square cen- 

 timetert is considered dangerous. It is admitted that 55 pounds in 

 this proportion is too extreme for safety, although, owing to peculiari- 

 ties of construction, tliis has been exceeded in some of the following 

 instances cited by M. Navier: 



Pounds. 



Pillars of the dome of the Invalides, Paris 32. 55 



Pillars of St. Peter's, Kome 36. 08 



Pillars of St. Paul's, Loudou 42. 70 



Columns of St. Paul-hors-les-Murs, Rome 43. 58 



Pillars of the tower of St. Merrl, Paris 64. 85 



Pillars of the dome of the Pautheon, Paris 61. 94 



M. Navier includes an estimate of 99.25 pounds for the church of La 

 Toussaut a Angers, which is in ruins, and so not a convincing example. 

 It thus appears that the resistance in some daring structures is from 

 33 to 44 pounds, and only rises to nearly 65 in two instances. M. 

 Eiffel cites the Washington Monument, which in its simplicity and 

 boldness he considers remarkable. In M. Navier's estimates given for 

 the" greatest feats of architectural engineering in the Old World, this 



"From the Atlantic Monthly, June, 1889; vol. lxiii, pp. 721-727. 

 tA square centimeter is about two- fifths of an inch on a side. 



