O Sleepless as the river under thee,
Vaulting the sea, the prairies' dreaming sod,
Unto us lowliest sometime sweep, descend
And of the curveship lend a myth to God.

HART CRANE, "TO BROOKLYN BRIDGE"

W ho can resist the majestic power of bridges? They
have been enshrined in children's jingles and cele-
brated by poets as symbols almost godlike in their
vault through space. The Pons Augustus in Rimini
declares the glory of Roman engineering as tri-
umphantly as the great aqueducts; the An-Chi
Bridge at Chao Chou, Hopei, China, tells us much
of the Sui Dynasty, just as London Bridge (for-
ever falling down) evokes the densely packed medi-
eval city, or St. Bénézet's Pont d'Avignon ("l'on
y danse") expresses the power of the medieval
monastic orders. For though architecture is con-
cerned with creating man's spaces, its skeleton,
tendon and bone, derive from structure. And the
bridge is precisely such a structural system, dis-
played in space in all its logic, purity, and grace.

A sure sign that a great new structural principle
has been born is the evolution of a new bridge
system. Such was the case with John A. Roebling's
Brooklyn Bridge ( 1869-1883), when its powerful
piers and spidery suspension cables declared the
strength of steel in tension. Its descendant are
San Francisco's dramatic Golden Gate Bridge and
the Hudson's regal George Washington Bridge.
But a bridge can be a roof as well as road or floor.
Hints of such uses of steel in tension appear again
and again in Frank Lloyd Wright's projects, in
Matthew Nowicki's North Carolina State Fair
Building, and in Eero Saarinen's Yale Hockey
Rink. R. Buckminster Fuller tells us that with
present alloys it would be possible to erect a dome
spanning a distance of two miles; the shelter en-
closed beneath would cover all the monuments of
classic Rome under one massive tent.

As man learned the lesson of the spider, so he
has now solved the riddle of the egg, namely, that
strength can evolve from form. (A simple crease in
a sheet of paper makes it a rigid member.) The
mathematical system which allows us to predict the
behavior of shells dates back to 1821, when a French
mathematician, Augustin Louis Cauchy, derived the
basic differential equations for the theory of elas-
ticity. In 1833 two other Frenchmen, Lamé and
Clapeyron, applied it to membrane structures. In
this century the German optical manufacturer
Carl Zeiss discovered that equations for optics
applied to reinforced-concrete structure, and used
them to vault the Zeiss Works in 1924.

But man needs symbolic structures more than a
formula to comprehend new principles. For the
world of steel-skeleton structures, such a symbol
was Paris's Eiffel Tower, erected in 1889 by the
bridge builder Gustave Eiffel ( 1832-1923). For
the world of concrete shells, the great symbols
were the massive airship hangars erected at Orly,
France, in 1916 by the French engineer Eugène
Freyssinet and the thin ribbons of concrete span-
ning Alpine gorges designed by the Swiss engineer
Robert Maillart. The visions of Etienne-Louis Boul-
Lée and the surrealist bubble-and-egg fantasies of
Hieronymus Bosch are now equally within the
grasp of modern man. The circular Sputniks and
Explorers orbiting in space declare the sphere to
be the new form of the space age. Man in his age-
long conquest of space has triumphed by creating
a microcosmos of the very earth.

-203-