The ancients, who were chiefly guided in their medical notions by the simple operations of nature, attached great importance to the influence of the moon. As the stars directed their navigators, so did the planets in some degree regulate their other calculations. Finding that the state of the weather materially acted on our organism whether in health or in sickness, they attributed this influence to the appearance of the moon, which generally foretold the vicissitudes in the atmospheric constitution. Thus Hippocrates advises his son Thessalus to study numbers and geometry, as the knowledge of astronomy was indispensable to a physician, the phenomena of diseases being dependent on the rising or the setting of the stars. Aristotle informs his disciples that the bodies of animals are cold in the decrease of the moon, that blood and humours are then put into motion, and to these revolutions he ascribes various derangements of women. To enter into these medical opinions would be foreign to the present purpose, but the notions of the ancients regarding lunar influence in other matters are curious. Lucilius, the Roman satirist, says that oysters and echini fatten during lunar augmentation; which also, according to Gellius, enlarges the eyes of cats: but that onions throw out their buds in the decrease of the moon, and wither in her increase, an unnatural vegetation, which induced the people of Pelusium to avoid their use. Horace also notices the superiority of shell-fish in the increase. Pliny not only recognises this influence on shell-fish, but observes, that the streaks on the livers of rats answer to the days of the moon's age; and that ants never work at the time of any change: he also informs us that the fourth day of the moon determines the prevalent wind of the month, and confirms the opinion of Aristotle that earthquakes generally happen about the new moon. The same philosopher maintains that the moon corrupts all slain carcasses she shines upon; occasions drowsiness and stupor when one sleeps under her beams, which thaw ice and enlarge all things; he further contends, that the moon is nourished by rivers, as the sun is fed by the sea. Galen asserts that all animals that are born when the moon is falciform, or at the half-quarter, are weak, feeble, and shortlived; whereas those that are dropped in the full moon are healthy and vigorous. In more modern times the same wonderful phenomena have been attributed to this planet. The celebrated Ambroise Pare observed, that people were more subject to the plague at the full. Lord Bacon partook of the notions of the ancients, and he tells us that the moon draws forth heat, induces putrefaction, increases moisture, and excites the motion of the spirits; and, what was singular, this great man invariably fell into a syncope during a lunar eclipse.