What lover ever had eyes to see the blemishes of his mistress? What lover ever ceas’d to admire his mistress’s beauty? This is another pernicious effect of learning; it occasions a sourness of temper. Philosophers think themselves wise in every thing; ’tis a difficult matter to persuade them that they every day injure their health by their manner of living; you may advise, intreat, and even scold them, it will be all to no purpose; they impose upon themselves a thousand different ways; some by too great a confidence in their strength, others by the hopes of impunity from the punishments being delayed; others again by the deceitful defence of the power of habit, and others again by the still more deceitful example of other men’s good luck; others by other motives; and all, by that steady adherence to their purpose, which they think becoming in a man of virtue, are so blinded, that they are not affected by future sufferings, and hardly even by those they have already incurred. I shall not however neglect my duty as a monitor, and if I should fail of success, it will be at least some merit to have attempted in a design of so much utility. Preservatives are to be offered to such of the studious as are still in health, and remedies to those who have impair’d their constitutions. The sure and only preservative is for the mind to be often unemploy’d, and the body to labour. This does not hold with regard to all men of learning; there are some whose meditations should be disturb’d upon no account whatever. DESCARTES frames a world, NEWTON revolves the whole system of the universe in his mind, MONTESQUIEU makes laws for all nations; let no body interrupt them, let all nature be silent, they labour for us, let the good of the people be the supreme law; they were born to cultivate those studies. But how few are there, whose labours are of such consequence? Most studious men lose their time, and break their constitutions to no purpose; one makes a collection of common-place topicks, another embellishes such as are threadbare, a third anxiously investigates matters of no utility, others make trifles the subject of laborious researches, and all are equally unmindful of the unprofitableness and danger of their pursuits. But be vigilant for their good; knock at their doors; rouse them from their lethargy; make them, whether they will or no, lay aside their studies for hours together, and let their minds not be totally abandoned to idleness, but recreated by gentle ease, whilst their strength is restored by exercise. At the beginning of my discourse I displayed the advantages of exercise: let it therefore be observed as an inviolable rule by the learned, to dedicate an hour or two every day to walking, that the lungs may be recreated by a free use of the air, that the stagnant humours may be thrown off, perspiration renewed, the limbs strengthened, and the nerves repaired. BOERHAAVE chose for this purpose the hour before dinner. Nor is walking