1911 Encyclopædia Britannica (1911)
“ In all styles, in less important work, the mullions are often simply plain chamfered, and more commonly have a flat hollow on each side. In larger buildings there is often a bead or bowtel on the edge, and often a single small column with a capital; these are more frequent in foreign work than in English. Instead of the bowtel they often finish with a sort of double ogee. As tracery grew richer, the windows were divided by a larger order of mullion, between which came a lesser or subordinate set of mullions, which ran into each other. ”
