Letter 90 — On the Part Played by Philosophy in the Progress of Man (§32)

“But Posidonius again remarks: “Democritus is said to have discovered the arch, whose effect was that the curving line of stones, which gradually lean toward each other, is bound together by the keystone.” I am inclined to pronounce this statement false. For there must have been, before Democritus, bridges and gateways in which the curvature did not begin until about the top.”