Of the refreshment afforded by the arrangement which I have hinted at, we obtain perhaps a most decisive converse evidence from that kind of sleep which is not healthy; and which, like all morbid states, is a deviation from the natural condition. How little repose is experienced on awaking from a sleep in which we have done little else than go over afresh the cares, the wearisome duties, the perturbations and struggles of the previous day; a kind of sleep which is well known by those who go to bed over-tired, over-excited, too weary to sleep, or, when sleeping, dreaming of labour.* One form of this over-fatigue is well known by literary men who retire to rest with their minds surcharged with the subject of some particular composition. Our illustrious townsman, Southey, gave an excellent admonition to a friend of mine who was writing a poem, - " Be sure when you dream of your subject, to lay your work aside for a few days." This advice was founded on his own experience. When that against which he warned my friend happened to himself, he made it a rule to engage in some other research. The secret of this is the unnatural excitement of a part of the nervous system, so that its action continues when it ought to subside. Every body must have felt the difficulty of getting rid of an impression on going to sleep, which, either from the vividness of its first presentation, or from the anxious emotions related with it, or simply from its long entertainment by the mind, continues in spite of our will. Such impressions bear a close analogy to those which are sometimes left on the mere organs of sense. When the eye has become fixed on a luminous object, the image remains for a time on the retina, even after the eyelids are closed. Loud and long continued sounds continue to echo in the ear, such as the roll of a carriage, etc. Analogous to these also is that feeling of oscillatory movement left in the body after tossing on the sea.

* "Atque in qua ratione fait contenta magis mens In somnis eadem pleramqne videmur obire: Causidici causas agere, et componere leges; Induperatores pugnare, ac praelia obire; Nautae contractnm cum ventis cernere bellum; Nos agere hoc autem, et naturam quaerere rerum Semper, et inventam patriis exponere chartia."

Lucret. Lib. IV.

Continuance then of the day's impressions and thoughts, may be considered as one of the forms of unhealthy dreaming. Another kind is that which derives its materials from bodily disturbances. These usually suggest emotions of gloom, fear, vexation, as well as scenes associated with such feelings, and derived from memory and imagination. Pressure upon some of the nerves of the skin in an uneasy posture, exposure of a part of the surface to cold, and indigestion, with its myriad morbid impressions, will give rise to the most frightful fancies. One hand cold and benumbed applied to the other, has suggested the idea of a visitant from the grave laying its deathy grasp on the sleeper in token of the truth of a communication which was the product of his own brain. As to the impressions derived from disorder of the internal organs, it must not be supposed that the painful and disagreeable dreams have not had such an origin, merely because the individual is unconscious of any such derangement; for, as we have already remarked, the sympathetic sensation often supersedes the primary impression. In the waking state, our minds may in like manner be oppressed by gloom and despondency, or filled with apprehensions of coming calamities, and the whole world "sicklied o'er" with the cast of dismal thought, though nothing has occurred at all warranting such feelings, and we ourselves are unconscious of anything wrong in the bodily organs. Yet, that these were in fault is proved by the dissipation of the unhealthy fears and anxieties, under the influence of measures which correct the corporeal functions.

Sometimes by the pressure of direct sensations from without, provided they are not too strong to arouse the sleeper, his dreams assume a happy character. Such may be the effect of faint and distant music, recalling delightful hours from the past, or suggesting imagery and actors from the world of poetry and romance.

It is a curious fact, that sometimes external impressions which have only been made during sleep, have also been revived in that state exclusively.* On the other hand, what has been heard in a half-dreaming state, may recur in a dream, and be afterwards remembered without the original source having been recognised. This may afford a clue to some mysterious verifications of dreams.

Of the material causes of dreams, none are more remarkable than the substances called narcotics, especially opium and belladonna. These drugs, while they annul the susceptibility of the sensory ganglia to outward impressions, have often a singularly exciting and perturbing influence on those portions of the brain which, at our last meeting, we pointed out as belonging to intellectual processes, and to the higher sentiments.

* An interesting case of this kind is related by Dr. Abercrombie in his work on the Intellectual Powers.

Nowhere are the effects of opium described with more power and eloquence than in the Confessions of an English Opium Eater; and I therefore shall not apologize for reading you more than one extract from that singularly interesting work.

"Oh! just, subtle, and mighty opium! that to the hearts of poor and rich alike, for the wounds that never heal, and .for the 'pangs that tempt the spirit to rebel,' bringest an assuaging balm; eloquent opium i that with thy potent rhetoric stealest away the purposes of wrath; and to the guilty man, for one night, givest back the hopes of his youth, and hands washed pure from blood; and to the proud man a brief oblivion for ' wrongs unredressed, and insults unrevenged;' that summonest to the chancery of dreams, for the triumph of suffering innocence, false witnesses; and confoundest perjury, and dost reverse the sentences of unrighteous judges; - thou buildest upon the bosom of darkness, out of the fantastic imagery of the brain, cities and temples beyond the art of Phidias or Praxiteles,- beyond the splendour of Babylon and Hecatompylos; and 'from the anarchy of dreaming sleep' callest into sunny light the faces of long buried beauties, and the blessed household countenances, cleansed from the ' dishonour of the grave.' Thou only givest these gifts to man; and thou hast the keys of paradise, Oh! just, subtle, and mighty opium!"