spring of an arch

spring of an arch
Springing Spring"ing, n. 1. The act or process of one who, or that which, springs. [1913 Webster]

2. Growth; increase; also, that which springs up; a shoot; a plant. [1913 Webster]

Thou blessest the springing thereof. --Ps. lxv. 10. [1913 Webster]

{Springing line of an arch} (Arch.), the horizontal line drawn through the junction of the vertical face of the impost with the curve of the intrados; -- called also {spring of an arch}. [1913 Webster]

The Collaborative International Dictionary of English. 2000.