The word convex means curving out or bulging outward.

Convex

The word convex means curving out or bulging outward.

"It is desirable, however, on account of economy of expense and of water, that all ditches should be as nearly straight as possible, and to save distance it is sometimes necessary to build up the ditch upon a mound or, if the depression to be crossed it too great, to construct a flume."—Government Printing Office, 1897

Section of Raised Ditch

"It is desirable, however, on account of economy of expense and of water, that all ditches should be…