(43) For the central sun, hierarchy of angels, and concentric circles, see Dante, Paradiso, canto xxviii. For the words of St. Thomas Aquinas, showing to Virgil and Dante the great theologians of the Middle Ages, see canto x, and in Dean Plumptre's translation, vol. ii, pp. 56 et seq.; also Botta, Dante, pp. 350, 351. As to Dante's deep religious feeling and belief in his own divine mission, see J. R. Lowell, Among my Books, vol. i, p. 36. For a remarkable series of coloured engravings, showing Dante's whole cosmology, see La Materia della Divina Comedia di Dante dichiriata in vi tavole, da Michelangelo Caetani, published by the monks of Monte Cassino, to whose kindness I am indebted for my copy. Let us look into this vast creation--the highest achievement of theology--somewhat more closely. Its first feature shows a development out of earlier theological ideas. The earth is no longer a flat plain inclosed by four walls and solidly vaulted above, as theologians of previous centuries had believed it, under the inspiration of Cosmas; it is no longer a mere flat disk, with sun, moon, and stars hung up to give it light, as the earlier cathedral sculptors had figured it; it has become a globe at the centre of the universe. Encompassing it are successive transparent spheres, rotated by angels about the earth, and each carrying one or more of the heavenly bodies with it: that nearest the earth carrying the moon; the next, Mercury; the next, Venus; the next, the Sun; the next three, Mars, Jupiter, and Saturn; the eighth carrying the fixed stars. The ninth was the primum mobile, and inclosing all was the tenth heaven--the Empyrean. This was immovable--the boundary between creation and the great outer void; and here, in a light which no one can enter, the Triune God sat enthroned, the "music of the spheres" rising to Him as they moved. Thus was the old heathen doctrine of the spheres made Christian. In attendance upon the Divine Majesty, thus enthroned, are vast hosts of angels, who are divided into three hierarchies, one serving in the empyrean, one in the heavens, between the empyrean and the earth, and one on the earth. Each of these hierarchies is divided into three choirs, or orders; the first, into the orders of Seraphim, Cherubim, and Thrones; and the main occupation of these is to chant incessantly--to "continually cry" the divine praises. The order of Thrones conveys God's will to the second hierarchy, which serves in the movable heavens. This second hierarchy is also made up of three orders. The first of these, the order of Dominions, receives the divine commands; the second, the order of Powers, moves the heavens, sun, moon, planets, and stars, opens and shuts the "windows of heaven," and brings to pass all other celestial phenomena; the third, the order of Empire, guards the others.