5. When I had recovered from my amazement at these things I asked, "What is this sound so strong and so sweet that fills my ears?" "This," he replied, "is the melody which, at intervals unequal, yet differing in exact proportions, is made by the impulse and motion of the spheres themselves, which, softening shriller by deeper tones, produce a diversity of regular harmonies. Nor can such vast movements be urged on in silence; and by the order of nature the shriller notes sound from one extreme of the universe, the deeper from the other. Thus yonder supreme celestial sphere with its clustered stars, as it revolves more rapidly, moves with a shrill and quick strain; this lower sphere of the moon sends forth deeper notes; while the earth, the ninth sphere, remaining motionless, [Footnote: Therefore without sound.] always stands fixed in the lowest place, occupying the centre of the universe. But these eight revolutions, of which two, those of Mercury and Venus, are in unison, make seven distinct tones, with measured intervals between, and almost all things are arranged in sevens. [Footnote: Latin, _qui numerus_ (that is, _septem_) _rerum omnium fere nodus est_. Literally, "which number is the knot of almost everything." The more intelligible form in which I have rendered these words seems to me to convey their true meaning, and my belief to that effect is confirmed by reading what several commentators say about the passage.] Skilled men, copying this harmony with strings and voice, have opened for themselves a way back to this place, as have others who with excelling genius have cultivated divine sciences in human life. But the ears of men are deafened by being filled with this melody; nor is there in you mortals a duller sense than that of hearing. As where the Nile at the Falls of Catadupa pours down from the loftiest mountains, the people who live hard by lack the sense of hearing because of the loudness of the cataract, so this harmony of the whole universe in its intensely rapid movement is so loud that men's ears cannot take it in, even as you cannot look directly at the sun, and the keenness and visual power of the eye are overwhelmed by its rays." While I marvelled at these things, I ever and anon cast my eyes again upon the earth.