Springing

Rules that use the word

How the pointed arches are drawn. Draw a pointed arch from two centres on the springing line. With the centres at the springings, the arch is equilateral; with centres beyond them, a lancet; with centres between them, a drop arch. Late Gothic added arches of four centres and the reversed curve of the ogee.

Pointed arches reach any height on any span. A round arch must rise half its span, so arches of different spans on one springing line have crowns at different heights. A pointed arch can be given any rise at least half its span, so arches of different widths can all be made to reach the same height.

The Derand–Blondel rule for abutments. To find how thick the pier of an arch must be, divide the intrados into three equal parts; draw a line from the springing through the first division, and produce it beyond the springing by its own length. A vertical through the end of that line marks the outer face of the pier.

Raise the dome on a drum. Lift the dome on a cylindrical or polygonal drum pierced with windows between the ring of the pendentives and the springing of the dome, to light the centre of the church and to make the dome visible from afar.

Ad quadratum: a section as high as it is wide. Proportion the cross-section of a church from the square: let the total height to the crown of the nave vault equal the total width, and take the heights of the aisles and the springing of the vaults at whole divisions of that square.

The horseshoe arch. Carry the curve of the arch beyond the semicircle, so that the opening at the springing is narrower than its greatest width.

Where it appears in the book

In the chapters The Arch, Vaults, Domes, Romanesque and Gothic, The Islamic World, Renaissance and Baroque, The Americas.

Nearby in the glossary

Spandrel panel · Specus · Spolia · Springer · Squinch · Steel frame · Stela · Step rings