SQUINCH  , possibly a corruption of

sconce (French equivalents are pendentive, trompe), the term in architecture applied to a corbelling out by means of arched rings in stone thrown across the angles of a square tower, to carry an octagonal spire or a dome . The earliest examples are found in the palaces of Serbittan and Firuzabad constructed by the Sassanian dynasty (A.D . 350-450), and in the mosque at Damascus, where it takes the form of a niche . In early French Romanesque work a small niche with additional rings above is employed; a greater importance is sometimes given by small shafts at the sides, of which there are examples in the Coptic churches of Egypt, and in France in the cathedral at Le Puy and the church of St Martin at Dijon .