equate

v. t. [ imp. & p. p. Equated; p. pr. & vb. n. Equating. ] [ L. aequatus, p. p. of aequare to make level or equal, fr. aequus level, equal. See Equal. ] To make equal; to reduce to an average; to make such an allowance or correction in as will reduce to a common standard of comparison; to reduce to mean time or motion; as, to equate payments; to equate lines of railroad for grades or curves; equated distances. [ 1913 Webster ]

Palgrave gives both scrolle and scrowe and equates both to F[ rench ] rolle. Skeat (Etymol. Dict. ). [ 1913 Webster ]

Equating for grades (Railroad Engin.), adding to the measured distance one mile for each twenty feet of ascent. --
Equating for curves, adding half a mile for each 360 degrees of curvature. [ 1913 Webster ]