What is "invention of the cross"

Invention \In*ven"tion\, n. [L. inventio: cf. F. invention. See Invent.]

1. The act of finding out or inventing; contrivance or construction of that which has not before existed; as, the invention of logarithms; the invention of the art of printing.

   As the search of it [truth] is the duty, so the invention will be the happiness of man.
   --Tatham.

2. That which is invented; an original contrivance or construction; a device; as, this fable was the invention of Esop; that falsehood was her own invention; she patented five inventions.

   We entered by the drawbridge, which has an invention to let one fall if not premonished.
   --Evelyn.

3. Thought; idea.
   --Shak.

4. A fabrication to deceive; a fiction; a forgery; a falsehood.

   Filling their hearers With strange invention.
   --Shak.

5. The faculty of inventing; imaginative faculty; skill or ingenuity in contriving anything new; as, a man of invention.

   They lay no less than a want of invention to his charge; a capital crime, . . . for a poet is a maker.
   --Dryden.

6. (Fine Arts, Rhet., etc.) The exercise of the imagination in selecting and treating a theme, or more commonly in contriving the arrangement of a piece, or the method of presenting its parts.

   Invention of the cross (Eccl.), a festival celebrated May 3d, in honor of the finding of our Savior's cross by St. Helena.