As we have seen throughout this book, one way that mathematics enters directly into poetry is through cosmology, which tracks the origin, creation and development, and sometime the future or fate of the whole world. The heavens seem to be a dome, half a sphere, sometimes blue brushed with clouds or the rose of dawn or the gold of sunset, and sometime black spangled with stars. Across the sky, the sun and moon and planets (and the odd comet) trace the great circle of the ecliptic, which then collects and orders the constellations of the Zodiac. By the sea or on the sea, the horizon, the visible boundary of earth, exhibits another great circle; and the sun and moon are spheres. Divine geometry! Days and months and years depend on the circuits of heavenly bodies, and the cycles are expressed as seasons: birth, maturity, withering, rebirth. Rivers seem to be great circles on earth, replenishing and sometimes threatening; mountains (and birds) seem to be middle terms between ourselves and the heavens, and caves (and snakes) middle terms between the living and the dead. A cave with a river running through it is a double portent, like a sky with a rainbow. Forests are habitations and labyrinths, where we may dwell or lose ourselves. The aim of cosmology is to provide explanations and reveal the meaningfulness of the world: mathematical order, periodicity, symmetry, number and figure, generally play an important role in these accounts.