_New York Industrial Exhibition exterior and interior views of another iron building in hall-form—nainely, the industrial-exhi bition building erected in New York in 1853—are given in Fignres 8 and 9 05/. 6). The ground-plan of this boldly-constructed, light, and elegant building of iron and glass was in the form of a Greek cross, between the arms of which additional one-storied structures of triangular ground-plan were introduced; so that the proper plan of the building took the form of an octagon. The diameter of the entire area, exclusive of the entrances, was 365Y, feet. In the centre of the cross a large dome, sixteen-sided in ground-plan, was supported upon slender iron columns; it was i6o feet in diameter by I22Y, feet in height to the vertex. The arms of the cross, 149 feet total width, were divided into three aisles of nearly equal width, which were arranged like those of a basilica, or so that the middle aisle was higher than the side aisles. The centre aisle, moreover, was clear to the roof, while the side aisles, with flat roofs, had galleries, and were thus two-storied. Each arm of the cross was flanked by two towers 69 feet high by i4Y, feet in diameter, which contained the staircases leading to the galleries, the principal stairways being near the dome Cfig. 9).
The lower floor had, in all, one hundred and ninety octagonal columns, of 27 feet height and 7Y, inches diameter, with walls from 3Yi. to io inches in thickness; the upper floor bad one hundred and forty-eight columns, of i7,i< feet height. These columns were connected by cast- and wrought iron lattice girders, partly to give stiffness and partly to support the gal leries, while semicircular open-work arches served for the support of the roofs over the centre aisle, the angles being filled in with open ornamenta tion. The cupola of the dome was supported by thirty-two iron arches. The roofs over the aisles, as well as the cupola, were boarded, and covered with tin. The exterior of the whole was pinted with oil-color of a bronze shade, the arches and other prominent portions being gilded. The total weight of the cast iron.was 1475 tons; of the wrought iron, 295 tons. The total area, including galleries, was 25o,000 square feet, and there were 55,000 square feet of glazed surface.
Sydenhain Oystol io to 14 give exterior and interior views, together with some of the details, of the most imposing and largest of iron buildings—namely, the Crystal Palace, built by Joseph Paxton, at Svdenham, in the southern part of London. This immense iron structure was really re-erected from the Hyde Park Exhibition Building of 1851, changes in the dimensions, and also architectural improvements, being made in it when transported to the new site. Among these alterations, the total length was decreased by about 25 feet, and an additional story was placed over the facade next the park, increasing the height by about 4o feet. The building was commenced in the summer of 1852, and was opened in the summer of 1854 for the permanent exhibition of articles of industry and art of all times and of all nations. The main, or centre,
aisle is r2o feet wide and 190 feet high; each side-transept, 72 feet wide and r56 feet high; while the total length, without the side-wings, is 16101.1. feet—including them, over 2oo4 feet—and the total height, 385 feet. There are five galleries placed one over another in the main transept, but elsewhere there are two. Figure 12 (j5/. 6) gives an interior perspective view of one of the upper galleries; the exterior of all these galleries is seen in Figure ro. All the walls and roofs are glazed. The roofs are supported by large curved lattice girders, as seen in the interior view (fig. II). The details given in Figures 13 and 14 show how the bottom iron columns in the different galleries are connected by flanges and bolts.
The Eifel TO7Cer. —The most remark-able of all iron structures is the Eiffel Tower (pi. 5, fig. 3), erected in Paris to serve as a leading feature in the International Exhibition of 1889. As projected, it is extraordinary not only on account of its great height (3oo meters, or 984 feet)—which is nearly twice that of the Washington Monument, formerly considered the highest artificial structure in the world—but because it is entirely of iron. It is in the form of an open framework or lattice-work, and, tak-ing into consideration the material employed and the type of the construction, it probably combines the highest attainable strength with the least possible weight. These elements are of prime importance in a work of such unpre cedented height; and when the enormous amount of wind-pressure it will be called on to withstand is considered, the suitability of the open framework —which opposes the least possible amount of surface—will be at once ap parent. It stands on four great " legs," or lattice columns, each placed at the angle of a square whose sides are 375 feet long. At a point 4So feet above the ground the legs meet at what is called " the middle landing-," and from this elevation upward it tapers like any ordinary structure of its kind. Near the summit is a balcony for observation. The tower is ter minated by a dome, which, in turn, is surmounted by a smaller dome, around the base of which is placed a small balcony for the use of those who may be venturesome enougrh to mount to the very top. The four columns forming the base are joined by circular arches, and at this level, its frame work- resting upon the crown of the arches and upon the columns, is erected a balcony called " the first landing." As the architectural effect depends largely upon leaving unobstructed the central space beneath the arches, the stairways and elevators by which visitors will be able to ascend and descend must be placed in the legs. The total weight of the tower will be 15,400,000 pounds, or 6875 tons.