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regard to spectral illusions. It seems to have the stage entirely to themselves. imply that the mind can create light Sensations are shut out, and ideas having, and project it from within upon the as it were, the house to themselves, riot retina, for it is only by light that a true and revel within at their pleasure. In picture can there be formed. It seems this lies the explanation of dreams. It also to imply that the mind first creates is not exactly that we confound ideas the spectre, then projects it upon the with sensations, but that no sensations retina, and from the retina receives it are present. Thought follows thought, back again, probably with more of a according to the usual laws of associasensational character than it possessed tion, like the ever-shifting scenes of a before. That this is really involved in panorama, and we live for the time in the theory may be made manifest. The a purely ideal world. It is probable, picture said to exist on the retina must moreover, that during our sleep our have some cause. That cause is nothing ideas become more vivid, just because real—nothing in the external world, for our attention is not distracted nor disspectres are allowed, on all hands, to turbed. Our whole mind is concenhave no actual objective existence. We trated upon them. The outer world does must seek for it, therefore, in the mind. not divide with the inner world our Nor can we believe that a vague idea mental energy. The latter monopolises would be represented by a definite and it all, and accordingly rises into greater distinct picture on the optic nerve; the prominence. This is probably, the reaidea must be the counterpart, as it is son why we remember some of our the cause, of the retinal painting. Con- dreams so well, and remember them, sciousness, however, does not reveal, in too, as peculiarly vivid and real-like; the case of spectral illusions, first, an while the fact of our forgetting so many idea in the mind, and then that idea of our sleeping thoughts may be taken projected into the outer world, and then as a proof that they were not more vivid returning to the mind in an objective than many of those waking thoughts form. Moreover, nature never acts in which we forget so soon too. such a way-it is simpler in all its But in our dreams everything seems processes.

to take an objective form. There apI hesitate, therefore, to go so far as the pears to be not merely a process of distinguished optician, and believe that thought, but an actual outside world. in every case of spectral illusion there We see men walking ; we hear them is a picture on the retina which is the speaking; we join with them in convercause of the deception in the mind. sation. Mountains and streams, or, it But the facts which have been adduced may be, palaces, and towers, and temples, warrant us to believe that ideas fre- surround us on every side. There is a quently become so vivid as to be mis- stage on which the visionary actors taken for sensations; and this alone is strut. This is generally regarded az sufficient to account for the phenomena. the peculiar and mysterious element in

In our waking state, we generally dreams. But it is not really peculiar discriminate accurately enough between or mysterious. In all our thinking we our sensations and our ideas, and that give to our thoughts an objective form, just because we are always conscious of though they stand out more distinct and both at the same time. The genuine more fully defined in our dreaming than sensations which are constantly pouring in our waking states, on account of the in upon us through every one of our absence of the disturbing element of senses keep our ideas in their proper sensation. In all thinking we are conplace. But in sleep it is different; our scious not of our thoughts, but of their senses are then, in a great measure, objects. But these objects belong to sealed. The only sensations which reach the outer world, and are therefore us are of a dull indistinct character. always thought of as existing there. thought is such a representation of it as the nerves, and in the brain, which only memory or imagination supplies. We require the excitement to be developed think of its great outlines, of its snowy in consciousness ? There are several peak, of the scenery amid which it lifts circumstances which strengthen this itself aloft. It stands before the mind suspicion into a belief. as a picture. It is not a mere thought No physical influence perishes all at in the brain : there is a thought in the once. Some men say that no physical brain, but it is of a mountain existing influence once created ever perishes. in Switzerland, and of this alone are we The vibrations of the atmosphere excited conscious. In every thought there is a by sound continually diminish, but never representation less or more distinct of cease. In like manner, may not the the thing thought of, and such repre- effect produced upon the nerves of sentations in our sleep form. dreams. sense by the objects of sense, whether In truth, our day dreams illustrate our these be vibrations and vibratiuncles, as night dreams. Absent men, when walk- Dr. Hartley held, or something else, coning along the street, or sitting by their tinue, though in a diminished and dimifire-side, may frequently be seen com- nishing degree, after the sensation has placently to smile, or to knit their brows, disappeared ? We know that the sensaor to clench their hands; and the secret tional influence remains, and is even felt of it is, that they have been placed by for a moment after the object is withtheir own thoughts amid scenes and drawn. A dazzling body may be discircumstances which have had such tinctly seen after the eyes are shut. A reality to them as to excite these phy- burning stick rapidly whirled round sical manifestations of pleasure or an appears an unbroken ring of light; noyance. There is nothing, therefore, which can be accounted for only by peculiarly mysterious in the objective supposing that the sensation produced form which our thoughts take in dreams, by the object, when at one point of the as this is a condition of all thinking. circumference, has not vanished before

In these mental facts, as we shall it reaches it again. The length of time afterwards see, lies the explanation of the sensation remains has even been almost every case of spectral illusion made the subject of calculation. It is There is, however, another circumstance, said to have been found by M. D'Arcet, half mental and half physical, worthy of a French philosopher, that the impresnote.

sion of light continued on the retina It is a singular, and it may be a sig about the eighth part of a second after nificant fact, that all our various sensa- the luminous body was withdrawn. Is tions may, in some measure, be produced there, then, anything to prevent us supby one common agent, electricity. When posing that the sensation may remain in this marvellous influence is transmitted the organ even after it has disappeared along the several nerves of special sense, from the consciousness, and that the it excites the sensation peculiar to each, organ only requires to be stimulated by and may be made to produce, in the electricity, or excited by a blow, to send same individual, and at the same time, a faint sensation into the mind ? flashes of light, crackling sounds, a pecu- There are some facts to give probaliar taste, a prickling feeling, and a phos- bility to the supposition. Mr. Boyle phoric smell. In a similar manner a has mentioned an individual who conbox on the ear will produce a ringing tinued for years to see the spectre of the sound; a blow on the eye, a spark of sun when he looked upon bright objects, light. In all these cases it is probably and this fact appeared so interesting and the violent stimulus which is given to inexplicable to Locke, that he consulted the nerve which is the proximate cause Sir Isaac Newton regarding its cause. of the sensation. And may not that. The great philosopher in his reply lead us to suspect that feeble sensational stated an experiment which he had made eyes.” After looking at the sun reflected excitement of a fever may so stimulate in a mirror, and then going into the the organ of memory that knowledge dark to observe the circles of light left long lost is regained. Languages spoken by it vanishing away, on the third occa- in infancy, but forgotten for many years, sion on which the experiment was re- may be fluently spoken again during peated, he saw to his amazement the delirium; long passages of poetry or spectre of the sun shining in the dark prose learnt at school, but never thought as vividly as he had seen it in the mirror. of since, may come back with all the He afterwards discovered that, so often freshness of yesterday, in similar ciras he went into the dark and thought cumstances. Stray sentences of a foreign of the sun, “as when a manlooks tongue accidentally heard, but heard only “ earnestly to see a thing which is diffi- to be forgotten, will recur to the memory, "cult to be seen," he could make the and be repeated with such accuracy as spectre return, and, the oftener he tried to make those around the bed of the the experiment, the easier it became. delirious patient marvel where such liteBy-and-by he discovered that, if he rature was acquired. In such cases—and looked upon any bright object, or even they are by no means uncommon-the upon a book," he saw upon it a bright excitement of the organs of memory round spot like the sun." These solar revives the faded recollection : in like, phantasms had now become somewhat manner, may not the excitement of the troublesome to the philosopher, and it nerves and ganglia of sense revive the was only by remaining a good deal in faded sensation? If it be so, have we the dark, and employing his mind upon not in this an explanation, not only of other subjects, that he got rid of the the facts to which I have referred, but spectre he had called up. It was some also, in some measure, of the spectral months before his cure was complete. illusions of fever, of delirium tremens,

This curious narrative, which is quite and of an excited state of the imain accordance with well-known facts in gination ? optics, seems to prove that, when a very We have, then, arrived at these results: strong impression is made upon the —that all thought is objective and organs of sense, it may continue to pictorial ; that ideas and sensations are exist there after the object is withdrawn, so closely allied that the one frequently and even when the sensation produced takes the place of the other ; that many by it has ceased ; and further, that this causes may give to our ideas peculiar lingering impression may be again quick- freshness and force ; that sensational inened into a sensation, either by the fluences do not perish in the organ the presence of an object in some respects moment they disappear from conscioussimilar to the original one, or by the ness; and that these may be excited so mind being directed towards it, or by as again to dawn upon the mind. I both these agencies together. In short, believe these simple and certain facts the organs of sense may be stimulated will explain almost all cases of spectral by an influence either from within or illusions, saving those which arise enfrom without, and thus an old sensation tirely from a morbid condition of the be brought back to life.

organs of sense. Let us look at some Some of the facts of memory afford a examples, dividing them into those which strong corroboration of this view. Ideas, have their seat in the organs of sense though absent from the consciousness, and those which have their seat in the are not lost to it; they are in some mind. mysterious way treasured up by memory, I. There are many cases of illusion to be reproduced when required. No which depend entirely upon a morbid one particle of knowledge, it is said, is state of the organs of sense. During a ever utterly lost. Knowledge quite ir- cold we have not unfrequently a ringing recoverable in ordinary circumstances sound in our ears. Some people are

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evidently arises from an irritable state of the auditory nerves. In like manner there are people who, from a diseased condition of the lenses of their eyes, see everything distorted—others who see everything out of its due proportions — others who see everything in a false colour. There are cases of men seeing everything inverted, and other cases of men seeing everything double ; but, indeed, the wonder is, that we all do not see objects inverted and double, as the structure of our eyes would lead us to expect. The state of the eye in which we lose sight of half of every object at which we look is more rare and more alarming. Dr. Wollaston, who experienced this defect of vision twice himself, informs us that after taking violent exercise he suddenly found that he could see but half of a man whom he met, and that, on attempting to read the name of Johnson over a door, he saw only SON, the commencement of the name being wholly obliterated from his view. Dr. Conolly mentions a gentleman who, when recovering from measles, saw objects diminished to the smallest possible size; and a patient mentioned by Baron Larrey, on recovering from amaurosis, saw men as giants, and everything magnified in a proportionate degree. In all such cases there is no mental illusion, but the diseased organ presents objects to the mind differently from what it would in its state.

II. There are cases of illusion which originate partly in the morbid condition of mind and partly in a morbid condition of the organism.

Spectral illusions of this kind may be artificially induced. Let a person drink any intoxicating liquor till he causes delirium tremens, and he will be haunted by devils. Let him eat opium, and he will probably see visitors of a more pleasing aspect swimming before his eyes. In like manner, persons labouring under a brain fever see visions, sometimes of an agreeable, but more frequently of a horrible kind. But such spectral sights are not confined to those who are under the influence of

sons experience them almost daily when under no such influence. A few cases will illustrate their nature, and enable us afterwards to inquire into their cause.

Sir David Brewster, in his interesting letters on Natural Magic, mentions a lady, a friend of his, who was frequently haunted by spectres. At first she was thoroughly deceived by them, but ultimately was able, at least on some occasions, to distinguish between real and phantom appearances. On one occasion, when sitting in the drawing-room on one side of the fire-place, she saw a deceased friend moving towards her from the window at the further end of the room. The spectre approached the fireplace, and sat down in a chair opposite' to that occupied by her. Thoroughly convinced it was an illusion, after gazing at it for some time, she summoned up courage to advance toward it, and seat herself in the same chair. The apparition remained till she boldly sat down, as it were in its lap, and then it vanished. Sir David mentions that the lady had a morbidly sensitive imagination, and that her health was in a disordered state during the period of these visitations. Her health gradually improved, and her spectral visitors disappeared.

Dr. Abercrombie, who is well known to have been a most careful and cautious observer of facts, mentions, in his interesting chapter on “Spectral Illusions," an old gentleman, who for some years before his death never sat down to dinner without the impression that he was surrounded by a number of friends, dressed in the fashion of fifty years ago. He mentions another gentleman who was so haunted by spectres that, if he met a friend in the street, he was at a loss to know whether it was really his friend or only his apparition. Dr. Hibbert tells us of a man who, having heard of the sudden death of an old and intimate acquaintance, and being deeply affected by it, went out to walk in a court attached to his house, when the figure of his friend started up before him in a dress which he had known him frequently to wear. Dr. Ferriar describes

eyes.” After looking at the sun reflected excitement of a fever may so stimulate in a mirror, and then going into the the organ of memory that knowledge dark to observe the circles of light left long lost is regained. Languages spoken by it vanishing away, on the third occa- in infancy, but forgotten for many years, sion on which the experiment was re- may be fluently spoken again during peated, he saw to his amazement the delirium ; long passages of poetry or spectre of the sun shining in the dark prose learnt at school, but never thought as vividly as he had seen it in the mirror. of since, may come back with all the He afterwards discovered that, so often freshness of yesterday, in similar ciras he went into the dark and thought cumstances. Stray sentences of a foreign of the sun, “as when a man looks tongue accidentally heard, but heard only “ earnestly to see a thing which is diffi- to be forgotten, will recur to the memory, “cult to be seen," he could make the and bo repeated with such accuracy as spectre return, and, the oftener he tried to make those around the bed of the the experiment, the easier it became. delirious patient marvel where such liteBy-and-by he discovered that, if he rature was acquired. In such cases and looked upon any bright object, or even they are by no means uncommon-the upon a book," he saw upon it a bright excitement of the organs of memory round spot like the sun.” These solar revives the faded recollection : in like, phantasms had now become somewhat manner, may not the excitement of the troublesome to the philosopher, and it nerves and ganglia of sense revive the was only by remaining a good deal in faded sensation? If it be so, have we the dark, and employing his mind upon not in this an explanation, not only of other subjects, that he got rid of the the facts to which I have referred, but spectre he had called up. It was some also, in some measure, of the spectral months before his cure was complete. illusions of fever, of delirium tremens,

This curions narrative, which is quite and of an excited state of the imain accordance with well-known facts in gination ? optics, seems to prove that, when a very We have, then, arrived at these results: strong impression is made upon the —that all thought is objective and organs of sense, it may continue to pictorial ; that ideas and sensations are exist there after the object is withdrawn, so closely allied that the one frequently and even when the sensation produced takes the place of the other ; that many by it has ceased ; and further, that this causes may give to our ideas peculiar lingering impression may be again quick freshness and force; that sensational inened into a sensation, either by the fluences do not perish in the organ the presence of an object in some respects moment they disappear from conscioussimilar to the original one, or by the ness; and that these may be excited so mind being directed towards it, or by as again to dawn upon the mind. I both these agencies together. In short, believe these simple and certain facts the organs of sense may be stimulated will explain almost all cases of spectral by an influence either from within or illusions, saying those which arise enfrom without, and thus an old sensation tirely from a morbid condition of the be brought back to life.

organs of sense. Let us look at some Some of the facts of memory afford a examples, dividing them into those which strong corroboration of this view. Ideas, have their seat in the organs of sense though absent from the consciousness, and those which have their seat in the are not lost to it; they are in some mind. mysterious way treasured up by memory, I. There are many cases of illusion to be reproduced when required. No which depend entirely upon a morbid one particle of knowledge, it is said, is state of the organs of sense. During a ever utterly lost. Knowledge quite ir- cold we have not unfrequently a ringing recoverable in ordinary circumstances sound in our ears. Some people are

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