Nocturnal lucubrations, which are hurtful upon many accounts, must have their place amongst the causes of disorders; for whilst a great part of the night is spent in study, sufficient time is not allow’d for sleep; nor does a gentle slumber succeed meditation; a circumstance which I have already lamented: for the oscillations of the fibres of the brain still continue, and that full ease of the internal senses is wanting which alone is capable of repairing our lost strength. They likewise pitch upon an unreasonable time for sleep; for nature has assigned the first approach of night as the proper time for beginning to repose; the night invites to sleep as well as the unwholesome air, and to this end its darkness and silence contribute: besides, the nocturnal air is cold and moist, and, when the sun retires, most animals feel their strength diminish’d, and night forces some of them to sleep even against their inclinations, as it does many plants. The night air is so unfavourable to study, that the celebrated VAN SWIETEN knew a gouty man, in whom the slightest application of mind, and even the reading of a letter, after sun-set, occasion’d a fit of the gout. Nor should we forget that study forces the blood into the brain, and that nothing can be more dangerous than to study in bed; for both sleep, and the posture of the body in sleep, increases the quantity of blood in the skull. Therefore nocturnal studies produce all those disorders which the want of rest gives rise to; the organs of sense are principally affected; their strength is exhausted, the fibres are either worn or agitated by violent motions; hence arise an incoherent series of thoughts, a luxuriant imagination, deliriums, dreadful head-achs, and, finally, a total privation of sleep, scarce to be cur’d by remedies, and which often occasions fatal disorders. The injuries of watching are increased by the ill effects of candles, which infect the air by their gross vapour, so pernicious to the lungs, the eyes, and the nerves. It is, therefore, the highest advantage imaginable to go to bed betimes, and rise early in the morning. _Aurora musis amica_: Aurora favours the muses. The close air, which they always use, is hurtful; but I shall speak of the air hereafter. Nor should their dirtiness be forgotten, as some learned men, entirely neglecting the care of their bodies, and not at all sollicitous about cleanliness, disgust others, and bring upon themselves those disorders which proceed from obstructed perspiration: for how can that skin perspire, whose pores are stopped up with dirt. Most of them are extremely faulty with respect to their teeth, which, being filled with putrid filth, and exhaling a most nauseous stench, first infect all the adjacent parts, and the very saliva of the sick person; soon after cause violent pains, and at last, falling before the time, leave the stomach destitute of the powerful aid of mastication.