herringbone pattern
An ingenious system used by Filippo as part of his technique to do away with the need for an elaborate centering, is therefore essential to the dome’s structure. In On Architecture Alberti later describes this technique as being essential for building a vault without centering, because connections bind the weaker components to the stronger ones. He compares the result to the human body, in which Nature “joins bone with bones and binds the flesh with tendons, introducing connections in all directions in length, breadth, depth and slantwise.” Where exactly Filippo learned of the herringbone bond is one of the dome’s unsolved mysteries. The pattern had of course been known to masons and bricklayers for many centuries. The Romans made extensive use of the bond they called opus spicatum, and the pattern is also found in the half-timbered brick walls of Tudor houses in England. In both these cases, however, it is decorative rather than structural; indeed, the Romans used it only in ornamental paving on the floors of their villas. Slightly farther afield, systems of interlocking brickwork similar to that in the cupola in Florence can be found in certain Persian and Byzantine domes, leading some scholars to speculate that Filippo may have visited these lands. This hypothesis is not improbable given the trade link with Asia Minor (which was so well known to Italians as early as the thirteenth century that Marco Polo did not consider it worth describing) as well as Filippo’s many “lost years” between 1401 and 1418. He may also have gained secondhand knowledge of these domes from merchants returning from the East (King, 2000).