Youth, or Adolescence, in general, is that happy period of human life, which commences from childhood ; continues as long as the fibres increase in dimensions or firmness ; and terminates at full growth : among the Romans, it was computed from the age of 12 to 25, in males, and to 21, in females. In modern times, the term adolescence, includes the age of from 15 to 25 years, and sometimes to 30.

During this important stage of our existence, the principal revolutions take place, both with respect to mind and body. While the latter progressively acquires muscular energy, and adopts a more soliddeportment, the faculties of the former begin to unfold ; and the young member enters into society, with all the advantages which arise from the tender regard, interest, and indulgence, evinced by the generality of mankind, towards inexperienced youth.

As it would be incompatible with our limited plan, to enter into a disquisition respecting all the mental and bodily imperfections, and diseases, incident to young persons of either sex; or to analyze the changes taking place during the transition from the period of childhood to that of puberty, we shall here discuss only the dangerous influence of the power of imagination, on the juvenile character.

None of the mental faculties exhibit such interesting and diversified phenomena, as that of Imagination. While this powerful agent is restrained within due li mits, it often supplies the place of a benevolent guide, through the intricate meanders of life, where we frequently meet with more appearance than reality ; and in which it is of the utmost importance to be impressed with a due and lively sense of the good and the beautiful, as well as of virtue and truth. On the contrary, no sooner are the boundaries of the imagining faculty transgressed, than we are involuntarily led to submit to this dreadful tyrant, who is capable not only of disturbing our repose and happiness, but even to deprive his victims of life. Hence, it should be one of the most necessary maxims of intellectual nature, always to guard against this formidable power ; and to regulate its reciprocal influence ; so that we may maintain a certain superiority. But, in order to evince the essential necessity of adopting this rule of practical life, and at the same time to demonstrate the danger attending the neglectof it, especially to youth, we shall quote an instance related by Prof. Hufeland, in one of his admired Popular Essays, in German; of which no translation has yet appeared.

A student at Jena, about 16 years of age, having a weak and irritable nervous frame, but in other respects healthy, left his apartments during twilight, and suddenly returned with a pale, dismal countenance; assuring his companion that he was doomed to die in 36 hours, or at 9 o'clock in the morning of the second day. This sudden change of a cheerful young mind naturally alarmed his friend; but no explanation was given of its cause. Every attempt at ridiculing this whimsical notion was fruitless; and he persisted in affirming that his death was certain and inevitable, A numerous circle of his fellow-students soon assembled, with a view to dispel those gloomy idens, and to convince him of his folly, by arguments, satire, and mirth. He remained, however, unshaken in bis strange conviction ; being apparently inanimate in their company, and expressing his indignation at the frolics and witticisms applied to his peculiar situation. Nevertheless, it was conjectured that a calm repose during the night would produce a more favourable change in his fancy ; but sleep was banished, and the approaching dissolution engrossed his attention during the nocturnal hours. Early next morning, he sent for Prof. Hufeland, who found him employed in making arrangements for his burial; taking an affectionate leave of his friends ; and on the point of concluding a letter to his father; in which he announced the fatal catastrophe that was speedily to happen. After examining his condition of mind and body, the Professor could discover no remarka-ble deviation from his usual state of health, excepting a small contracted pulse, a pale countenance, dull or drowsy eyes, and cold extremities : these symptoms, however, sufficiently indicated a general spasmodic action of the nervous system, which also exerted its influence over the mental faculties. The most serious reasoning on the subject, and all the philosophical and medical eloquence of Dr. HUFELAND, had not the desired effect; and, though the student admitted that there might be no ostensible cause of death discoverable, yet this very circumstance was peculiar to his case; and such was the inexorable destiny of his fate, that he must die next morning, without any visible morbid symptoms. - In this dilemma, Dr. H. proposed to treat him as a patient. Politeness induced the latter to accept of such offer; but he assured the physician, that medicines would not operate. As no time was to be lost, there being only 24 hours left for his life, Dr. H, deemed proper to direct such remedies as prove powerful excitants; in order to rouse the vital energy of his pupil, and to relieve him from his captivated fancy. Hence he prescribed a strong emetic and purgative; ordered blisters to be applied to both calves of the legs, and at the same time stimulating clysters to be administered. Quietly submitting to the Doctor's treatment, he observed, that his body being already half a corpse, all means of recovering it would be in vain. Indeed, Dr. H. was not a little surprized, on repeating his visit in the evening, to learn that the emetic had not, or but very little, operated; and that the blisters had not even reddened the skin. Now the case became more serious; and the supposed victim of death began to triumph over the incredulity of the Professor, and his friends. Thus circumstanced, Dr. H. perceived, how deeply and destructively that mental spasm must have acted on the body, to produce a degree of insensibility from which the worst consequences might be apprehended. - All the inquiries into the origin of this singular belief, had hitherto been unsuccessful. Now only, he disclosed the secret to one of his intimate friends, namely, that on the preceding evening he had met with a white figure in the pa sage, which nodded to him ; and, in the same moment, he heard a voice exclaiming: " the day after to-morrow, at nine o'clock in the morning, thou shalt die." - He continued to settle his domestic affairs; made his will; minutely appointed his funeral; and even desired his friends to send for a clergyman; which request, however, was counteracted. Night appeared; and he began to compute the hours he had to live, till the ominous next morning: his anxiety evidently increased with the striking of every clock within hearing. Dr. H. was not without apprehension, when he recollected instances in which mere imagination had produced melancholy effects. But, as every thing depended on procrastinating, or retarding that hour in which the event was predicted ; and on appeasing the tempest of a perturbed imagination, till reason had again obtained the ascendancy, he resolved upon the following happy expedient: Having a complaisant patient, who refused not to take the remedies prescribed for him (because he seemed conscious of the superior agency of his mind over that of the body), Dr. H. had recourse to laudanum, combined with the extract of hen-lane : 20 drops of the former, and two grains of the latter, were given to the youth, with such effect, that he fell into a profound sleep, from which he did not awake till eleven o'clock on the next morning. Thus, the prognosticated fatal hour elapsed; and his friends waiting to welcome the bashful patient, who had agreeably disappointed them, turned the whole affair into ridicule. The first question, however, after recovering from this artificial sleep, was the hour of the morning on being informed, that his pre-sages had not hern verified by ex-perience, he assured the company, that all these transactions appeared to him not unlike a dream ; and he could not conceive how he had been subject to such folly. Since that period, he has enjoyed a per-fect state of health, and has been completely cured of his fancy.

There arc, nevertheless, several instances recorded, in which persons have truly predicted the day and hour of their death. In the 17th century, it was a fashionable practice among the higher classes, to apply to an astrologer, for learning the accurate duration of their lives. Such aberration from the human intellect. could be ascribed only to an absurd or defective sys-of education; when youth were not taught to discriminate between natural causes and effects ; or, when parents granted every species of indulgence, which alike excited their sensual desires, and pleased a wild, disordered imagiMany, indeed, are the gradations, in which that peculiar morbid sensation, generally termed irregutar fancy, displays itself un-different forms, even in mo-dern times, It cannot be denied, that the numerous phenomena of nervous disorders, especially the dined symptoms displayed by hypochondriacal and hysterical persons, doubtless originate chiefly from the same source. We often smile at such complaints as are supposed to arise from a diseased mind, but certainly not with jus-tire. In short, there is no disorder more to be dreaded, and none has a more solid foundation, than that in which the sensations of our material nature, and the ideas of our very existence, are in a manner unhinged : nay, it is incomparably more easy to sustain a real evil, than to be tormented by an imaginary one, the force and extent of which cannot be ascertained.