That is--'O thou _primum mobile_, thou cruel firmament, that with thy diurnal revolution (or revolution once in 24 hours round the axis of the equator) continually forcest along and whirlest all the celestial bodies from East to West, which _naturally_ would wish to follow the course of the sun in the zodiac from West to East.' This is well illustrated by a sidenote in the Ellesmere MS. to the passage in question, to this effect:--'Vnde Ptholomeus, libro i. cap. 8. Primi motus celi duo sunt, quorum vnus est qui mouet totum semper ab Oriente in Occidentem vno modo super orbes, &c. Item aliter vero motus est qui mouet orbem stellarum currencium contra motum primum, videlicet, ab Occidente in Orientum super alios duos polos[72].' That is, the two chief motions are that of the _primum mobile_, which carries everything round from East to West, and that of the fixed stars, which is a slow motion from West to East round the axis of the zodiac, to account for precession. This exactly explains the well-known passage in the Frankeleines Tale (C. T., F 1280):-- 'And by his eighte spere in his werking, He knew ful wel how fer Alnath was shove Fro the heed of thilke fixe Aries above That in the ninthe spere considered is.' Here the eight spheres are the eight inner spheres which revolve round the axis of the zodiac in an easterly direction, whilst the ninth sphere, or _primum mobile_, contained both the theoretical or _fixed_ first point of Aries from which measurements were made, and also the _signs_ of the zodiac as distinct from the _constellations_. But Alnath, being an actual star, viz, [alpha] Arietis[73], was in the _eighth_ sphere; and the distance between its position and that of the first point of Aries at any time afforded a measure of the amount of precession. Mr. Brae rightly remarks that Tyrwhitt's readings in this passage are correct (except that _eighte speres_ should be _eightespere_), and those of Mr. Wright and Dr. Morris (from the Harleian MS.) are incorrect. It may be as well to add that a later refinement was to insert a crystalline sphere, to account for the precession; so that the order stood thus: seven spheres of planets; the eighth, of fixed stars; the ninth, or crystalline; the tenth, or _primum mobile_; and, beyond these, an empyræan or theological heaven, so to speak, due to no astronomical wants, but used to express the place of residence of celestial beings[74]. Hence the passage in Milton, P. L. iii. 481:-- 'They pass the planets seven, and pass the fix'd, And that crystalline sphere whose balance weighs The trepidation talk'd, and that first mov'd.'