The Roman arch averted stress totally, preserving all the masonry in compression, in the keystone for the piers. Stone in compression has wonderful power, plus the Romans designed big arched bridges and aqueducts in significant figures. Extending their arch right into a tunnel, they invented the barrel vault, with which https://f004.backblazeb2.com/file/DigitalAsset/westhillmasonry/Hardscape-Contractors.html