A correspondent writes us that the excellent article on " Wakefulness," recently published in the SCIENTIFIC AMERICAN, does not meet his case, which he states is a common one with laboring men. His affliction is drowsiness. He says within the narrow circle of his acquaintance there are not less than three-fourths who are afflicted in the same way. This affection is a standing obstacle in the way of self-improvement; and our correspondent complains that his own acquisitions have been greatly limited on account of it, and desires to know what may be done to remedy the evil. We are well aware that drowsiness is a much more common complaint than wakefulness, and, in general, it is one, which, owing to the difficulty of inducing people to renounce long established habits, is hard to cure. The phenomenon of sleep is yet enveloped in profound mystery. Volumes have been written upon it; numberless experiments have been performed; and after all we know nothing whatever of its true character. Experiment has taught us, however, that drugs produce it when taken into the stomach, or otherwise conveyed into the system; that certain habits produce a greater desire for it than is natural; and that the will has power to resist its demands to a limited extent. The causes of sleep are then either natural, or unnatural, and the phenomenon is correspondingly morbid or healthy. The natural and healthy sleep, consequent upon exhaustion, can never be interfered with without greater or less damage to the general health in each instance. Unnatural drowsiness generally results from some error in the habits of living, or it is a constitutional defect. The latter is difficult to cure, but the majority of cases are not constitutional affections, and they are curable. Many cases of supposed abnormal drowsiness, are not abnormal at all. People who work hard all day, or who have been exposed to cold winds, are apt to feel sleepy when they find themselves comfortably housed in the evening, especially if they have indulged in a hearty supper. All these causes naturally induce sleep, and when the tendency to sleep is powerful it ought not to be resisted. Many will find the disposition to sleep postponed for several hours, by the substitution of a very light meal for the hearty one which is often taken at the close of the day's work. Others will find that this does not avail them, and that notwithstanding their abstemiousness, the drowsy god still asserts his sway. These people will have to submit, and either doze in their easy chairs or go to bed; but they need not on that account be deprived of time for study. They will almost invariably find that they can rise two or three hours earlier than other people, without inconvenience, and they will further find that their three morning hours before breakfast are as good as four in the evening after supper would be if they could keep awake and study. They may, at first, find some difficulty in waking at the proper time; an alarm clock will overcome that. They should not, at first, apply themselves to reading or study in these reclaimed morning hours, but should engage in some active occupation until the habit of thoroughly waking is established, after which in the majority of cases no inconvenience will be experienced. A feeling of drowsiness after eating is perfectly natural and healthy, but it is easy to see that over-eating might so intensify the feeling as to render it nearly impossible to resist it. Those troubled with this complaint, ought then to carefully 186 avoid over-eating at any time, and particularly so belore any period during which they desire to keep awake. In this, as in all other complaints, an ounce of prevention is worth a pound of cure. It will, we think, be rare that drowsiness will occur if perfectly regular hours for sleeping are observed; unless it is induced by a plethoric condition, conse- j quent upon high living, or a constitutional habit. Nevcrthe- j less, there are some simple remedies. One of the best is to wet the head suddenly and thoroughly with cold water. The shock will generally suffice to throw off the sleepy feeling. Strong tea or coffee will often aid in preventing drowsiness, but these are only temporay helps. A radical cure can only be attained by the correction of the habits, whatever they may be, that induce it. Temperance in eating as well as in drinking, regular hours, avoidance of too exhausting labor, must be observed. We do not advocate the use of drugs for this complaint. Each person so afflicted ought to make a j thorough examination of his habits of living, and in most j cases he will find the stomach to be the offending organ.