In the obscurity of the evening, or during the darkness of the night (particularly on those nights which are cloudy, and the darkness seems to rest on the ground), the difficulty with which we distinguish any object to which the attention is directed, is liable to induce a disordered state of the eye, the effects of which are very startling.
"The imperfect view which we obtain of such objects forces us to fix the eye more steadily upon them; but the more exertion we make to ascertain what they are, the greater difficulties do we encounter to accomplish our object. The eye is actually thrown into a state of the most painful agitation, the object will swell and contract, and partly disappear, and it will again become visible when the eye has recovered from the delirium into which it has been thrown."[46]
This illusion is increased by a disturbed condition of the pupil of the eye.
The pupil is surrounded by a muscle called the iris, by the contraction and dilatation of which the size of the opening is increased or diminished, and a greater or less amount of light admitted to the eye. On a dark night, or during the twilight, the pupil is dilated to its utmost extent, so that every available ray of light may enter. In this condition the eye is not able to accommodate itself to near objects, and they become more indistinct; shadowy, and confused.
Under these circumstances, an object to which the attention is strongly attracted, may appear to assume strange variations in form,—now increasing, now diminishing in size, now approaching nearer, now going further off, or anon disappearing altogether; and a bush, a guide-post, a stoop, &c., will seem as though it assumed the most startling changes in size and appearance. Add the effects of the imagination, and we shall at once perceive a source of the various goblins, boggards, and other strange sights which have been supposed to haunt many of our byeways and deserted places.
To illustrate this form of illusion: a man with whom we were acquainted tells the following tale:—When young, he, one evening, had a quarrel with his mother about some trifling affair, and in defiance of her grief and supplications he left home late at night, intending to enter the army. It was very dark and stormy, and as he proceeded along a bye-path, suddenly a tall object arrested his attention; startled, he stood still, when, to his utter horror and astonishment, the object increased in size, and seemed as though about to pounce upon him; it then vanished, and anon appeared again. Terrified beyond measure, and conceiving that Satan had waylaid him for forsaking his mother, the poor man fell on his knees, and exclaimed: "O good Lord Devil, do not take me, and I'll go back to my mother, and be a good lad!" It is unnecessary to dwell upon the goggle eyes burning with flames which he imagined Satan to possess; suffice it that he remained before the supposed devil some time, overcome with terror, when a blink of the rising moon showed that he was laid at the foot of the stump of a tree. Heartily ashamed of his fear, he rose up, slunk back home, and made peace with his mother.[47]
This will suffice as an example of the most degraded form of ghost-life with which our highways and byeways have been peopled by the superstitious and illiterate,—illusions which have arisen from the effects of a disturbed condition of the visual organ on an excited imagination. Burns humorously describes this variety of ghost in his "Address to the Deil:"
"Ae dreary, windy, winter night,
The stars shot down wi' sklentin' light,
Wi' you, mysel, I gat a fright,
Ayont the lough:
Ye like a rash-bush stood in sight
Wi' waving sugh.
"The cudgel in my nieve did shake,
Each bristled hair stood like a stake,
When wi' an eldricht stour, quaick—quaick—
Amang the springs,
Awa ye squatter'd like a drake,
On whistling wings."
Another form of illusion is induced by objects seen indistinctly when the mind is disturbed and pre-occupied by some powerful and painful emotion.