Light is therefore color, and shadow the privation of it by the removal of these rays of color, or subduction of power;
and these are to be found throughout nature in the ruling principles of diurnal variations.
The grey dawn, the yellow morning and red departing ray, in every changing combinations,
are constantly found to be by subduction or inversion of the the rays of their tangents.
-- J. M. W. Turner, 1818.