Section of Notre-Dame du Port
"It was in Central France, and mainly along the Loire, that the systematic development of vaulted church architecture began. Naves covered with barrel-vaults, sometimes of pointed section, appear in a number of large churches built during the eleventh and twelfth centuries, with apsidal and transeptal chapels and aisles carried around the apse, as in Notre-Dame du Port at Clermont-Ferrand. The thrust of these ponderous vaults was clumsily resisted by half-barrel vaults over the side aisles, transmitting the strain to massive side-walls."
A. D. F. Hamlin College Histories of Art History of Architecture (New York, NY: Longmans, Green, and Co., 1915)
Courtesy the private collection of Roy Winkelman