“Oh ye whose intellectual ministry Moves the third heaven.”—Carey.
[156] “The sun sees not, though circling all the world.”
[157] The spherical form of Earth, and the action of gravity at the earth’s surface, were commonplaces with the Greeks, as we have seen in Part I. of this book. Posidonius, Strabo, and other classical writers speak of the tides as following the revolution of the heavens, and having periods similar to those of the moon; Albertus Magnus and Aquinas ascribe them to the influence of the moon, and so does Dante himself in Par. xvi. 83.
[158] See Moore, Studies in Dante, II. “The Genuineness of the Quæstio de Aqua et Terra,” for a complete discussion of the question.
[159] V. N. xliii. 3-7.
[160] Conv. II. xiv. 244-217. “It is noble and lofty because of its noble and lofty subject, which is the movement of the heavens; it is lofty and noble because of its certainty, which is without flaw.”
[162] “The great wheels,” “eternal wheels,” “starry wheels.”
[163] “Swift, almost as the heaven ye behold.” Par. ii. 21.