Saturday, September 26, 2009

Firmitas, Utilitas, Venustas

In Julius Caesar's The Gallic Wars (58 BC), an excellent description is provided regarding the construction of a timber bridge across the Rhine:

"Even though he was confronted by the greatest difficultly for making a bridge because of the river's width, swiftness, and depth, nevertheless be decided that he had to make the effort or else not lead his army across. He used the following method for the bridge. At intervals of 2 feet, he joined pairs of timbers that were 1.5 feet thick, sharpened a bit at their bases, and measured for the depth of the river. Having lowered these into the river with machines, he fixed and rammed them down using pile drivers, not quite perpendicular in the manner of piles, but leaning forward and sloping so that they inclined with the natural flow of the river. In addition, he planned two piles opposite these at an interval of 40 feet downstream, fastened together in the same manner but turned into the force and flow of the river. These two rows were kept firmly apart by inserting into their tops beams 2 feet thick, which were the same length as the distance between the piles, and that were supported with pairs of braces at the outer side of each pile. As a result of this combination of holding apart and clamping together, so great was the stability of the work and its character that the greater the force of the water rushing against it, the more tightly its parts held fastened together. These beams were interconnected by timbers laid at right angles, and then these were floored over with long poles and wickerwork. In addition, piles were driven at an angle into the water on the downstream side, which were thrust out underneath like a buttress and joined with the entire structure to take the force of the river. Similarly others were emplaced a little bit above the bridge so that if tree trunks or vessels were sent by the barbarians to knock down the structure, the force of those objects might be diminished by these defenses and prevent the bridge from suffering harm.

Ten days after the timber began to be collected the bridge was completed and the army was led across."

Caesar (i.e., his engineers) built the bridge not because it was militarily necessary but because he thought it would overawe the enemy with Roman might and ingenuity. This was more than engineering, which has purely pragmatic ends; it was an act of signification. As if to emphasize the fact, he burned his work of art eighteen days later after an aimless foray into Germany.

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