Squinch

squinch, in architecture, a piece of construction used for filling in the upper angles of a square room so as to form a proper base to receive an octagonal or spherical dome. It was the primitive solution of this problem, the perfected one being eventually provided by the pendentive. Squinches may be formed by masonry built out from the angle in corbeled courses, by filling the corner with a vise placed diagonally, or by building an arch or a number of corbeled arches diagonally across the corner. In Islamic architecture, especially in Persia, where it may have been invented, the squinch took the form of a succession of corbeled stalactites. It was also commonly used in the early churches of Europe and the East.

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squinch [skwinch]

(architecture)

A small arch across the interior corner of a structure to support a superimposed mass such as a dome or spire. Also known as squinch arch.

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squinch

squinch, 2

1. Corbeling, often arcuate, built at the upper corners of a structural bay to support its tangent, smaller dome or drum.

2. A small arch across the corner of a square room which supports a superimposed mass; also called a sconce.

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Squinch 

in architecture, a vaulted structural component consisting of parts of a cone or half or quarter of a spherical cupola. Squinches are usually employed for the transition from a square substructure to a round or polygonal superstructure and to a cupola or its drum. They are sometimes also used to support angular cupolas and oriels. Squinches were widespread in the medieval architecture of Southwest and Central Asia, the Transcaucasus, and Europe; in Russia they were used primarily in the 17th century.