Quaestiones Naturales

Is it because depth is the mother of darkness, so that it doth dim and mar the sunbeams before they can descend so low as it? As for the uppermost superficies of the water, because it is immediately affected by the sun, it must needs receive the white brightness of the light; the which Empedocles verily approveth in these verses:

A river in the bottom seems

By shade of color black;

The like is seen in caves and holes,

By depth, where light they lack.

Or, since the bottom of the sea and of great rivers is often full of mud, doth it by reflection of the sunbeams represent the like color that the said mud hath? Or is it more probable that the water toward the bottom is not pure and sincere, but corrupted with an earthy quality,— as continually carrying with it somewhat of that by which it runneth and wherewith it is stirred,—and the same settling once to the bottom causeth it to be more troubled and less transparent?