The author next treats of the planets, and the periods of their respective revolutions; of the stars, comets, winds, thunder, lightning, and other natural phenomena, concerning all which he delivers the hypothetical notions maintained by the ancients, and mentions a variety of extraordinary incidents which had occurred in different parts of the world. The third book contains a general system of geography, which is continued through the fourth, fifth, and sixth books. The seventh treats of conception, and the generation of the human species, with a number of miscellaneous observations, unconnected with the general subject. The eighth treats of quadrupeds; the ninth, of aquatic animals; the tenth, of birds; the eleventh, of insects and reptiles; the twelfth, of trees; the thirteenth, of ointments, and of trees which grow near the sea-coast; the fourteenth, of vines; the fifteenth, of fruit-trees; the sixteenth, of forest-trees; the seventeenth, of the cultivation of trees; the eighteenth, of agriculture; the nineteenth, of the nature of lint, hemp, and similar productions; the twentieth, of the medicinal qualities of vegetables cultivated in gardens; the twenty-first, of flowers; the twenty-second, of the properties of herbs; the twenty-third, of the medicines yielded by cultivated trees; the twenty-fourth, of medicines derived from forest-trees; the twenty-fifth, of the properties of wild herbs, and the origin of their use; the twenty-sixth, of other remedies for diseases, and of some new diseases; the twenty-seventh, of different kinds of herbs; the twenty-eighth, twenty-ninth, and thirtieth, of medicines procured from animals; the thirty-first and thirty-second, of medicines obtained from aquatic animals, with some extraordinary facts relative to the subject; the thirty-third, of the nature of metals; the thirty-fourth, of brass, iron, lead, and tin; the thirty-fifth, of pictures, and observations relative to painting; the thirty-sixth, of the nature of stones and marbles; the thirty-seventh, of the origin of gems. To the contents of each book, the author subjoins a list of the writers from whom his observations have been collected.