Mag., 1879) is that of a rectangular aperture, traversed by a cylindrical wave with aberration equal to cx 3 .

As if containing the OH group; this leads to the formula H 3 C C(OH): CX CO 2 C 2 H 5.

May be a simultaneous invariant of a number of different forms az', bx 2, cx 3, ..., where n1, n 2, n3, ...