* Henricus ab Heeres Observat. Medic. L. i. Obs. 2. p. 32 33. Wanley's Wonders, p. 625.

The same conclusion may be drawn from the relation of Caelius Rhodiginus, who informs us, that when he was twenty-two years of age, being busied in the interpretation of Pliny, while as yet the learned emendations of Hermolaus Barbarus on that excellent author had not performed to him all that was requisite, he was reading that place in the seventh book, which treats of those who grow up beyond the usual proportion which Nature has assigned. The word Ectrapeli, by which such persons were described by the Greeks, was of some trouble to him. He knew that he had read something concerning it, but not being able to recall the author, nor the book in which the word was mentioned, and fearing the imputation of unskilfulness, he retired with uneasiness of mind to sleep, when, his thoughts continuing still to employ themselves on the subject, he recollected the book, and even the page which he wanted *.

* Schotts Phys. Curios. L. iii. C. 25. p. 50. Cael. Rhod. Antiq. Lect. L. xxvii, C, 9. p. 1250. and Wanley's Wonders Ch. 23.

Persons are very commonly known to walk in their sleep over ridges and parapets, at which Mad Tom would have shuddered. Upon these occasions it appears, that they often act merely from recollection, since they stumble over objects placed in their way. The recollection, however, is often defective, and however circumspectly and steadily the persons may guard against danger in some parts, they often forget where it exists in others. The imagination is also generally so ascendant, that the judgment is not allowed time to act. The eyes of the person are frequently open, but objects which appear before them are usually unheeded, the mind being so absorbed by its own contemplations, as to be inattentive to impressions conveyed by the senses. Sometimes, however, the eyes continue, even in sleep, to present objects to the mind which engage its attention; as in the case of Johannes Oporinus, a printer, who, being employed one night in correcting the copy of a Greek book, fell asleep as he read, and yet ceased not to read till he had finished not less than a whole page, of which, when he awoke, he retained no recollection *.

The attention of the mind, in this case, appears to have been gradually withdrawn after the body began to sleep. This disposition to walk and act in sleep is usually considered as a disorder occasioned, according to the opinion of some persons, by a plethora, to which young men are chiefly liable: we may conceive in these cases the turgid and foaming blood to excite sensations which affect the mind: the disorder is understood to be curable by purging the primae viae †. Whatever be the remote cause which affects the mind on these occasions, it certainly affords to it an opportunity of displaying its superior powers of intelligence, raised and excited, as it were, by new sensations, and moving the body only- as an incumbrance to which it is chained. A similar but less remarkable effect is displayed, when, by an agitation of the spirits, persons are found to talk in their sleep, or to cry out and move, and even to execute their designs by external actions.

* Plater. Observ. L. i. p. 12.

† Levinus Lemnius describes these night-walkers as men of a relaxed habit of body, and great fervour and activity of mind, as chiefly young persons; observing that old persons, in whom the vital powers begin to flag, are incapable of the exertion. De Occult. Nat. Mirac. L. ii. C. 5.

There is another faculty of the mind distinct from those hitherto specified, if we may credit a singular relation of Mr. Halley, who declared to the Royal Society, that being carried by a strong impulse to visit St. Helena, in order to make observations on the southern constellations, being then twenty-four years of age, he dreamed, before he undertook the voyage, that he was at sea, sailing towards that place, and saw the prospect of it from the ship in his dream, which exhibited the perfect representation of that island, as it afterwards appeared on his approach. It is possible, that the picture was formed agreeably to the ideas of the island, which his correct mind had formed from the accounts of others which he might have heard or read. Every one, however, may probably have noticed instances, in which particular scenes appear, or particular events happen, of which a representation may seem before to have taken place in his mind; a circumstance certainly not easy to be explained, but upon the supposition of some presaging power of the mind; but of which the existence and limits are not sufficiently ascertained or defined, to authorize the ascribing of any prophetic intelligence to it, or to imply any design in Providence thereby to direct us, any farther than by such general intimations of the spiritual nature of the mind.

The unpleasant sensations occasioned by the incubus, or night-mare, are either accidental or habitual, and they appear to affect both mind and body. The former is often occasioned by the distension of the stomach with wind or crudities; and it is apt to prevail when people lie on their backs, for then the stomach, being dilated, presses the midriff and muscles of the breast most, and by that means encumbers the descent of the one and the expansion of the other, which are necessary to respiration, and thus the blood be-comes stagnant in the lungs.

The habitual night-mare is supposed to be occasioned by some acid lymph which disorders the spirits, and creates a paralytic or convulsive disposition of the nerves of the midriff and muscles, which press upon those of the windpipe, and produce the sense of strangling: hypochondriacal and scorbutic persons are particularly liable to these complaints.

It is doubtful, in some instances, whether dreams originate with the mind spontaneously summoning up its own ideas, or with the body prompting some sensation of solicitude. In the case of the existence of disorders in the body, the fearful or oppressive dreams which iudicate a disordered habit, need not necessarily be ascribed to the immediate operation of the body on the mind commencing in sleep, since the mind, sympathetically affected when awake *, may by its own reflections generate gloomy phantoms that scare it when the pains of sensation are suspended.

As for dreams which seem to argue a redundancy of health, it is at least disputable, whether they arise from an ardent imagination operating on the mind, or a full constitution of body, suggesting ideas to the imagination. The connexion which subsists between the mind and the body is so intimate, and their reciprocal influence so immediate, that it is difficult to discriminate the boundaries of their respective operations, and the only consideration of consequence, is the necessity of purifying the affections, and of subjecting the body to rules of temperance and self-command.

* Per consensum et legem consortia Levin, Lemn. de Occult. N. Mir. L. i. C.12.