Some, who allow darkness to be a cause of the sublime, would infer, from the dilatation of the pupil, that a relaxation may be productive of the sublime as well as a convulsion: but they do not, I believe, consider, that although the circular ring of the iris be in some sense a sphincter, which may possibly be dilated by a simple relaxation, yet in one respect it differs from most of the other sphincters of the body, that it is furnished with antagonist muscles, which are the radial fibres of the iris: no sooner does the circular muscle begin to relax, than these fibres, wanting their counterpoise, are forcibly drawn back, and open the pupil to a considerable wideness.

But though we were not apprised of this, I believe any one will find, if he opens his eyes and makes an effort to see in a dark place, that a very perceivable pain ensues.

And I have heard some ladies remark, that after having worked a long time upon a ground of black, their eyes were so pained and weakened, they could hardly see.

It may perhaps be objected to this theory of the mechanical effect of darkness, that the ill effects of darkness or blackness seem rather mental than corporeal: and I own it is true that they do so; and so do all those that depend on the affections of the finer parts of our system.

The ill effects of bad weather appear often no otherwise than in a melancholy and dejection of spirits; though without doubt, in this case, the bodily organs suffer first, and the mind through these organs.
SECTION XVII.
THE EFFECTS OF BLACKNESS.
Blackness is but a _partial darkness_; and therefore it derives some of its powers from being mixed and surrounded with colored bodies.