Part v. was to contain the general rules of astrology, with tables of equations of houses, dignities of planets, and other useful things which God and the Virgin might vouchsafe that the author should accomplish. Sections 36 and 37 tell us something about the equations of houses; but, in all probability, none (or, at least, no more) of this fifth Part was ever written. Tables of equations of houses, for the latitude of Toledo, are given in MS. Camb. Ii. 3. 3, at fol. 177, and elsewhere. Of the general rules of astrology we find in old MSS. somewhat too much, but they are generally in Latin; however, the Trinity MS. R. 15. 18 has some of them in English. On the whole, we have quite as much of Chaucer's Treatise as we need care for; and he may easily have changed his mind about the necessity of writing Part v; for we actually find him declaring (and it is pleasant to hear him) that 'natheles, thise ben observauncez of iudicial matiere & _rytes of payens, in which my spirit ne hath no feith_'; ii. 4. 36; (p. 192). § 25. SOURCES OF THE TREATISE. I next have to point out the sources whence Chaucer's treatise was derived. Mr. Halliwell, in a note at the end of his edition of Mandeville's Travels, speaks of the original treatise on the Astrolabe, written in Sanskrit, on which he supposes Chaucer's treatise to have been founded. Whether the Latin version used by Chaucer was ultimately derived from a Sanskrit copy or not, need not be considered here. The use of the Astrolabe was no doubt well known at an early period in India and among the Persians and Arabs; see the 'Description of a Planispheric Astrolabe constructed for Sháh Sultán Husain Safawí, King of Persia,' by W. H. Morley, in which elaborate and beautifully illustrated volume the reader may find sufficient information. Marco Polo says (bk. ii. c. 33) that there were 5000 astrologers and soothsayers in the city of Cambaluc, adding--'they have a kind of _Astrolabe_, on which are inscribed the planetary signs, the hours, and critical points of the whole year'; Marco Polo, ed. Yule, i. 399. Compare also the mention of the instrument in the 161st night of the Arabian Nights' Entertainments, where a translation which I have now before me has the words--'instead of putting water into the basin, he [the barber] took a very handsome astrolabe out of his case, and went very gravely out of my room to the middle of the yard, to take the height of the sun'; on which passage Mr. Lane has a note (chap. v. note 57) which Mr. Brae quotes at length in his edition. There is also at least one version of a treatise in Greek, entitled [Greek: peri tês tou astrolabou chrêseôs], by Johannes Philoponus, of which the Cambridge University Library possesses two copies, viz. MSS. Dd. 15. 27 and Gg. 2. 33. But it is clear, from his own words, that Chaucer followed the Latin, and I can point out[52] one of the Latin treatises to which he was very considerably indebted. This is the 'Compositio et Operatio Astrolabie,' by