Oddly enough, the construction of the Eiffel tower, with its dizzying latticework of interwoven steel beams, was made possible by earlier experiments in iron bridge construction in the late 1700s.
Prior to the use of these metals in construction, brick was the major building material. With its triangular truss construction, and four semicircular arches, you could say that the tower takes bridge building technology and stands it on its head.
If you look at the picture of the tower, you will notice the extensive use of triangles in the construction. It has been known since the ancient Greeks that the triangle is the strongest, lightest, and most rigid form in geometry.
Unfortunately, brick and masonry materials cannot easily be formed into free-standing triangles. In the 1860's, the Bessemer furnace made it possible to quickly and economically roll long steel beams called girders.
Because steel can be rolled into these long and slender beams, they were used to create triangular forms in the Eiffel Tower. These primary advantages, light weight relative to brick construction, and the triangular form, gave birth to this tower, and in fact, every sky piercing skyscraper you see. The Eiffel Tower was the tallest structure in the world until New York's Chrysler building was finished in 1930.
