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CHAPTER III.

OF SLEEP.

IN the admirable series of illustrations, by which a great philosophic genius, extending the argument of Paley, has deduced evidence of design in the universe from the coadaption of the laws by which classes of natural phenomena, that have no necessary dependence on each other, are regulated, the suitableness of the length of the day to the constitution of man and animals and plants has not passed without notice.

Mr. Whewell observes, in reference to sleep, "Man in all nations and ages has taken his principal rest once in twenty-four hours, and the regularity of this practice seems most suitable to his health, though the duration of the time allotted to repose is extremely different in different cases. So far as we can judge, this period is of a length beneficial to the human frame independently of the effect of external agents. In the voyages recently made into high northern latitudes, when the sun did not rise for three months, the crews of the ship were made to adhere with the utmost punctuality to the habit of retiring to rest at nine, and rising a quarter before six; and they enjoyed, under circumstances apparently the most trying, a state of salubrity quite remarkable. This shows that, according to the common constitution of such men, the cycle

of twenty-four hours is very commodious, though not imposed upon them by external circumstances."“No one can maintain, with any plausibility, that the period may be lengthened or shortened without limit. We may be tolerably certain that a constantly recurring period of forty-eight hours would be too long for one day of employment and one period of sleep with our present faculties; and all, whose minds and bodies are tolerably active, will probably agree that, independently of habit, a perpetual alternation of eight hours up, and four in bed, would employ the human powers less advantageously than alternations of sixteen and eight."

"The succession of exertion and repose in the muscular system, of excited and dormant sensibility in the nervous, appears to be fundamentally connected with the muscular and nervous powers, whatever the nature of these may be. The necessity of these alternations is one of the measures of the intensity of those vital energies; and it would seem that we cannot, without assuming the human powers to be altered, suppose the intervals of tranquillity which they require to be much changed *."

That sleep, the natural period of the alternation of which with a period of exertion, independent of, yet so curiously adjusted to the length of a diurnal revo

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* "The arbitrary quantity, the length of the physiological and of the astronomical fact, is the same. Can this have occured otherwise than by an intentional adjustment ?”—Whewell's Bridgewater Treatise, p. 37.

lution, Mr. Whewell has shown to be an additional proof of the existence of God, is felt by every one to prove His beneficence,-whether in the soothing influence, with which it steals over us, lapping the senses and tired thoughts in forgetfulness, or in the renovation, and alacrity of spirit, with which we rise refreshed from it.

Repose is not less necessary to the animal frame than exercise. The latter uses, the former restores. It is on their alternation and right balance that strength depends. We can give repose to a strained or weary limb by laying it horizontally and without motion, to an aching joint by a posture of ease and stillness, to the stomach by abstinence, but not by means exactly parallel to these, can we give rest to the mind. It is in vain that in complete bodily tranquillity, we strive to give composure and quiet to our waking thoughts, their play continues to excite, and disturb, and exhaust;-for mental rest, more is wanted, for the repose of the nervous system, there must be Sleep.

What is the condition of the mind during sleep? The first question which presents itself, on entering into this inquiry, is, whether the current of ideas is ever entirely suspended: whether that endless flow of changing thought, which characterizes our waking hours, is even in the deepest sleep stagnant and motionless. There are strong reasons for believing that such complete intermission of mental action does not take place.

We breathe, and the effort is probably voluntary, the call of a sensation, which we so relieve.

We compute the flight of time during sleep, and if we have business to transact that much interests our thoughts, wake at an unusual hour, before the required hour of waking, and out of the seemingly deepest repose. It is not, however, unlikely, that in this instance, where some kind of conscious observation must have been watching, our sleep has really been imperfect. Opposite as are waking and deep sleep, no two phenomena are more wonderfully chained together by links of insensible transition.

Many have thought that dreams belong to this intermediate state. Lord Brougham, who has given the most definite shape to this hypothesis, observes, after enumerating instances of lengthy dreams, the whole of which, however, must have been comprised in an infinitely short space of time, as they originated in the impression that awoke the dreamer, "There seems every reason to conclude that we only dream during the instant of transition into and out of sleep."

For my own part, I am disposed to adopt the opposite opinion, and think that in sleep we always dream; though we lose the recollection of those dreams (by far of course the greater number), which are not from their exciting nature more strongly impressed than common on our minds, or which do not occur so near waking as to be associated at no great remoteness with our waking thoughts. Either hypothesis, however, is equally unsusceptible of proof. What appears to

me most to merit attention in this subject is the fact of the non-interference of our dreams, whether occasional or constant, with our bodily or with our mental rest and refreshment. This, I think, is explained by, and explains the objects of, the most curious phenomena of dreaming.

In dreams, that which most strikes us are their monstrous and capricious combinations, and our want of surprise at their improbability. Thought suggests thought perfectly at random; the laws of mental crystallization seem suspended or confounded; any side of any element of thought appears capable of attracting the unlikeliest relation of another. Yet we seem to see nothing extraordinary in the fantastic

creations.

A check is absent in dreaming, which our waking reason uses. When awake we recollect our just relation to every event and person presented to our senses or to our thoughts: something like our true position is constantly before us. In dreams this is quite forgotten,-wife, children, home, are not ours; while the friends whom we have lost, our parents, long wept in the grave, meet and converse with us, as if they were our daily companions. Our fancy experiences no check from reality: the link which unites its operations with the past and the present and the future is temporarily unloosed.

The mind may be said in sleep to be put out of When we dream, the engine continues to work, but the whirl of thought has no bearing upon our

gear.