Chaucer's Works (ed. Skeat) Vol. III/Treatise on the Astrolabe Introduction

§ 1. The existing MSS. of the 'Astrolabe' are still numerous. I have been successful in finding no less than twenty-two, which I here describe. It is remarkable that, although many printed editions of the treatise have appeared, no first-class MS. has ever hitherto come under the notice of any one of the various editors. This point will appear more clearly hereafter.

§ 2. A.—MS. Dd. 3. 53 (part 2) in the Cambridge University Library. The 'Treatise on the Astrolabie' begins at fol. 212 of the MS. considered as a whole, but the folios are now properly renumbered throughout the treatise. The MS. is of vellum, and the writing clear and good, with a great number of neatly drawn diagrams, which appear wherever the words 'lo here thi figure' occur in the text. This MS. I have made the basis of the text, and it is followed with sufficient exactness, except when notice to the contrary is given in the Critical Notes.

This MS. is of considerable importance. The handwriting exactly resembles that in MS. B., and a comparison of these MSS. leads to the following results. It appears that MSS. A. and B. were written out by the same scribe, nearly at the same time. The peculiarities of spelling, particularly those which are faulty, are the same in both in a great many instances. It is also clear that the said scribe had but a very dim notion of what he was writing, and committed just such blunders as are described in Chaucer's Lines to Adam Scriveyn, and are there attributed to 'negligence and rape .' It is still more interesting to observe that Chaucer tells us that he had to amend his MSS. by 'rubbing and scraping' with his own hand; for MS. A. and B. differ precisely in this point, viz. that while the latter is left uncorrected, the former has been diligently 'rubbed and scraped' by the hand of a corrector who well knew what he was doing, and the right letters have been inserted in the right places over the erasures. These inserted letters are in the hand of a second scribe who was a better writer than the first, and who was entrusted with the task of drawing the diagrams. The two hands are contemporaneous, as appears from the additions to the diagrams made by the writer of the text. Unfortunately, there are still a good many errors left. This is because the blunders were so numerous as to beguile the corrector into passing over some of them. When, for example, the scribe, having to write 'lo here thy figure' at the end of nearly every section, took the trouble to write the last word 'vigure' or 'vigour' in nearly every instance, we are not surprised to find that, in a few places, the word has escaped correction. It further appears that some of the later sections, particularly sections 39 and 40, have not been properly revised; the corrector may very well have become a little tired of his task by the time he arrived at them. It must also be remembered, that such blunders as are made by a scribe who is not clear as to the meaning of his subject-matter are by no means the blunders which are most puzzling or most misleading; they are obvious at once as evident blotches, and the general impression left upon the mind by the perusal of this MS. is—that a careless scribe copied it from some almost perfect original, and that his errors were partially corrected by an intelligent corrector (possibly the author), who grew tired of his task just towards the end.

The order of the Conclusions in Part ii. differs from that in all the editions hitherto printed, and the MS. terminates abruptly in the middle of a sentence, at the words 'howre after howre' in Conclusion 40 (p. 223). A portion of the page of the MS. below these words is left blank, though the colophon 'Explicit tractatus,' &c. was added at the bottom of the page at a later period.

Certain allusions in the former part of the MS. render it probable that it was written in London, about the year 1400.

§ 3. B.—MS. E Museo 54, in the Bodleian Library, Oxford. This is an uncorrected duplicate of the preceding, as has been explained, and ends in the same way, at the words 'howre after howre,' followed by a blank space. The chief addition is the rubricated title—'Bred and mylk For childeren,' boldly written at the beginning; in the margin are the following notes in a late hand—'Sir Jiffray Chaucer'—'Dominus Gaufredus Chaucerus'—'Galfredi Chauceri Tractatus de Ratione et vsu Astrolabij ad Ludouicum filium.'

§ 4. C.—MS. Rawlinson, Misc. 1262, otherwise 1370 (leaves 22-42), in the Bodleian Library, Oxford.

This is a beautifully written MS., on vellum, with 38 pages of text, and 4 blank pages. It has the Conclusions in the same order as the preceding, six well-executed diagrams, and corrections on nearly every page. It is of early date, perhaps about A.D. 1420, and of considerable importance. It agrees closely with the text, and, like it, ends with 'howre after howre.' Some variations of spelling are to be found in the Critical Notes. In this MS. the Conclusions are numbered in the margin, and the numbers agree with those adopted in this edition.

§ 5. D.—MS. Ashmole 391, in the Bodleian Library. I have made but little use of this MS., on account of its being very imperfect.

§ 6. E.—MS. Bodley 619. This MS., like B., has the title—'Brede and Milke for children.' Like other good MSS., it ends sect. 40 with 'houre after houre.' But after this, there occurs an additional section, probably not genuine, but printed here (for the sake of completeness) as section 46; see p. 229. Cf. § 17.

At fol. 21 is an additional section, not found elsewhere, which is printed in the Notes; see p. 360. This Conclusion has some claims to our notice, because, whether genuine or not, it is translated from Messahala.

§ 7. F.—MS. 424, in the Library of Corpus Christi College, Cambridge. Very imperfect, especially at the beginning, where a large portion has been lost.

The Conclusions follow the right order, as in the best MSS.

§ 8. G.—MS. R. 15, 18, in the Library of Trinity College, Cambridge. This is a curious and interesting volume, as it contains several tracts in English on astrology and astronomy, with tables of stars, &c.

The copy of the 'Astrolabe' in this MS. is not a good one. It ends in Part ii. sect. 34, l. 14. The Conclusions are in the right order, and there are a few diagrams.

§ 9. H.—MS. Sloane 314, British Museum. A late MS. on paper, absurdly said in a note to be in Chaucer's handwriting, whereas it is clearly to be referred to the end of the fifteenth century.

§ 10. I.—MS. Sloane 261. This is an 'edited' MS., having been apparently prepared with a view to publication. Mr. Brae has made considerable use of it, and gives, in his preface, a careful and interesting account of it. He concludes that this MS. was written by Walter Stevins in 1555, and dedicated by him to Edward Earl of Devonshire; and that MS. H. was one of those which Stevins especially consulted, because it contains marginal notes in Stevins' handwriting. The contents of this MS. can be so well ascertained from Mr. Brae's edition that it is unnecessary to say more about it here. The Conclusions are arranged in the same order as in other MSS. that are not of the first class.

§ 11. K.—MS. Rawlinson Misc. 3, in the Bodleian Library, Oxford. On vellum, 49 folios, with rich gold capitals, beautifully ornamented; in a large clear handwriting, with red rubrics. Title—'Astralabium.' Begins—'Lityl lowys my sone,' &c.—and ends—'For þe mone meuyth the contrarie from other planetys. as yn here epicircle. but in none other maner'; see end of Part ii. sect. 35; p. 217. Order of Conclusions in Part ii. as follows; 1-12, 19-21, 13-18, 22-35; as in other late MSS. There are no diagrams, and the MS., though well written, may perhaps be referred to the latter half of the fifteenth century.

§ 12. L.—MS. Additional 23002, British Museum. A fair MS., on vellum, without diagrams; imperfect. See description of MS. R. in § 17. And see the Note on Part ii. sect. 3 (p. 360).

§ 13. M.—MS. E. 2 in the Library of St. John's College, Cambridge. Small MS. on vellum, without diagrams. The leaves have been misplaced, and bound up in a wrong order, but nothing is lost. I have printed from this MS. the last five words of sect. 40; also 41-43, and 41a-42b; besides collating it for the improvement of the text in sect. 44; sect. 45 is missing. I have also been indebted to it for the Latin rubrics to the Conclusions, which I have not found elsewhere. Several various readings from this MS. appear in the Critical Notes (pp. 233-241).

§ 14. N.—MS. Digby 72, in the Bodleian Library. From this MS. I have printed the text of sections 44 and 45 (pp. 226-9), but have made little further use of it.

§ 15. O.—MS. Ashmole 360, in the Bodleian Library. Late MS., on paper; former owner's name, Johan Pekeryng; without diagrams. There are evidently some omissions in it. But it includes sections 44 and 45, and I have given various readings from it in those sections (p. 240). It ends at the end of sect. 43a, with the words—'one to twelfe. & sic finis&apos;; see p. 232.

§ 16. P.—MS. Dd. 12. 51 in the Cambridge University Library. Small MS. on vellum; written in the fifteenth century. The text is by no means a bad one, though the spelling is peculiar. Some of the pages are very much rubbed and defaced. I have taken from it some various readings, recorded in the Critical Notes.

One point deserves particular attention. It not only contains the Conclusions of Part ii. in the right order, but continues it without a break to the end of Conclusion 43 (p. 225); at the end of which is the colophon—Explicit tractatus astrolabii.

§ 17. Q.—MS. Ashmole 393, in the Bodleian Library; on paper. Of little importance.

R.—MS. Egerton 2622, in the British Museum. A neat MS., but without diagrams. Contains: Part I. (except 15-23); Part II. §§ 1-12, 19-21, 13-18, 22-35, 41-43, 44, 45; 41a, 41b, 42a, 43a, 42b, 36, 37. Thus it has all the additional sections except 46; but 38-40 are missing. MS. L. contains the same sections in the same order; see § 12.

S.—MS. Addit. 29250. A poor MS., but remarkable for containing the scarce section no. 46; of which there is but one other copy, viz. that in MS. E (§ 6); cf. pp. 240, 241.

T.—MS. Phillipps 11955; at Cheltenham. On vellum; 31 leaves; said to be of the fourteenth century, which is improbable.

U.—MS. Bodley 68. Imperfect; ends at Part ii. § 36.

W.—MS. E Museo 116, in the Bodleian Library. A mere fragment.

X.—A MS. at Brussels, no. 1591. See F. J. Mone, Quellen und Forschungen, (Aachen, 1830); pp. 549-551.

§ 18. Of the above MSS., Mr. Brae describes H., I., and L. only, and does not seem to have made use of any others. Mr. Todd, in his Animadversions on Gower and Chaucer, p. 125, enumerates only four MSS., which are plainly A., P., F., and G. The rest seem to have escaped attention.

In addition to the MS. authorities, we have one more source of text, viz. the Editio Princeps, which may be thus described.

Th.—The edition of Chaucer's Works by Wm. Thynne, printed at London by Thomas Godfray in 1532. This is the first edition in which the Treatise on the Astrolabe appeared; it begins at fol. ccxcviii, back. The Conclusions in Part ii. are in the order following, viz. 1-12, 19-21, 13-18, 22-40; after which come 41-43, and 41a-42b. This order does not agree precisely with that in any MS. now extant, with the exception of I., which imitates it. It has some corrupt additions and exhibits many grave errors. All later editions, down to Urry's in 1721, contribute no new information. The few slight alterations which appear in them are such as could have been made without reference to MSS. at all.

§ 19. On comparing the MSS., it at once appears that they do not agree as to the order of the Conclusions in Part ii. The MSS. A., B., C. (which are unquestionably the oldest), as well as E., F., G., and P., adopt the order which appears in this edition, but which has never appeared in any previous edition. In all other editions we find the three sections 19-21 made to precede sections 13-18. Now we might here appeal to authority only, and say that the order in the oldest MSS. ought to be preferred. But it so happens that we can appeal to internal evidence as well, and there are two considerations which shew that the oldest MSS. are certainly correct. These are as follows. In the first place, sect. 18 amounts to finding the degree of the zodiac which souths with any star, and begins with the words 'Set the centre of the sterre upon the lyne meridional'; whilst sect. 19 amounts to finding the degree of the zodiac that rises with any star, and begins with the words 'Set the sentre of the sterre upon the est orisonte.' Clearly, these Conclusions are closely linked together, and one ought to follow the other. But, in all the editions, this continuity is broken. In the second place, the rubric of sect. 21 is—'To knowe for what latitude in any regioun,' &c.; whilst that of sect. 22 is—'To knowe in special the latitude of oure countray,' &c. Clearly, these Conclusions are closely linked, and in their right order. But, in all the editions, this continuity is again broken; and we have this absurd result, viz. that a proposition headed—'To knowe the degrees of the longitudes of fixe sterres' is followed by one headed—'To knowe in special the latitude of oure countray.' Hence we are enabled to draw a line, and to divide the MSS. into two classes; those in which the order of sections is correct, and those in which it has suffered misplacement, the number in each class being much the same. This gives us the following result.

First Class. A., B., C, (probably D.,) E., F., G., P.

Second Class. H., I., K., L., M., N., O., R.; to which add Th.

But this division immediately leads to another very curious result, and that is, a certain lack of authority for sections after the fortieth, which ends on p. 223.

A. ends with an incomplete sentence, in sect. 40, with the words—'howre after howre.' B., C. end exactly at the same place.

E. ends sect. 40 with the same words; and, after this, has only one additional section (46), which is, in my opinion, spurious; especially as it does not appear in Messahala, of which more anon.

D., F., and G. all fail at an earlier point.

In none of the first-class MSS. (excepting P., which terminates with section 43) is there a word about umbra recta or umbra versa.

Even in the second class of MSS., we find H. breaking off at sect. 36, and K. at sect. 35; so that the sections on the umbrae rest only on MSS. I. (obviously an edition, not a transcript), L., M., N., O., P., and R. Putting aside the first of these, as being 'edited,' we have but six left; and in the first four and the last of these we find that the additional Conclusions appear in a certain order, viz. they insert 44 and 45 (on the 'mene mote') between three sections 41-43 on the 'umbrae' and five other sections 41a-42b on the same.

§ 20. This at once suggests two results. The first is, that, as this gives two sets of sections on the 'umbrae,' we can hardly expect both to be genuine; and accordingly, we at once find that the last five of these are mere clumsy repetitions of the first three; for which reason, I unhesitatingly reject the said last five as spurious. This view is strikingly confirmed by MS. P.; for this, the only first-class MS. that is carried on beyond section 40, contains the first three sections on the 'umbrae' only. The second result is, that if the first three sections on the 'umbrae' are to be received, there is good reason why we should consider the possible genuineness of sections 44 and 45 on the 'mene mote,' which rest very nearly on the same authority.

Now the sections on the 'mene mote' have in their favour one strong piece of internal evidence; for the date 1397 is mentioned in them more than once as being the 'root' or epoch from which to reckon. In most cases, the mention of a date 1397 would lead us to attribute the writing in which it occurs to that year or to a later year, but a date fixed on for a 'root' may very well be a prospective one, so that these sections may have been written before 1397; an idea which is supported by the line 'behold whether thy date be more or lasse than the yere 1397'; sect. 44, l. 5. But I suspect the date to be an error for 1387, since that [see Somer in Tyrwhitt's Glossary] was really the 'rote' used by Nicholas Lenne. In either case, I think we may connect these sections with the previous sections written in 1391. Besides which, Chaucer so expressly intimates his acquaintance with the subjects of these sections in the Canterbury Tales, that we may the more readily admit them to be really his. There is still less difficulty about admitting the first three sections (41-43) on the 'umbrae,' because we find similar matter in the treatise of Messahala, from which, as will appear, he derived so much. And hence we may readily conclude that, in the second part, the first forty sections, found in the oldest MSS., are certainly genuine, whilst sections 41-43, as well as 44 and 45, have every claim to be considered genuine also. This need not, however, force us to accept the remaining sections, since they may easily have been added by another hand; a circumstance which is rendered the more probable by the fact that sections 41a-42b merely repeat 41-43 in a more clumsy form, and by the consideration that, if genuine, they should have occupied their proper place immediately after sect. 43, instead of being separated from the former set. As to sect. 46, I pronounce no decided opinion; there is but little to be said either for or against it, and it is of little consequence.

§ 21. But admitting the genuineness of sections 40-45, it at once becomes evident that there are two distinct gaps or breaks in the continuity of the treatise; the first between 40 and 41; and the second between 43 and 44. A little consideration will account for these. Looking at the Canterbury Tales, we observe the very same peculiarity; at certain points there are distinct breaks, and no mending can link the various groups together in a satisfactory manner. This can be accounted for in part by our knowledge of the fact that the poet died before he had completed the proper linking-together of the tales which he had more or less finished; but I think it also shews him to have been a fragmentary worker. To suppose that, upon reaching Conclusion 40, he suddenly turned to the sections upon the 'umbrae,' which are at once more easy to explain, more suitable for a child, and illustrative of a different and more practical use of the Astrolabe, seems to me natural enough; and more probable than to suppose that anything is here lost. For, in fact, it is to the very MSS. that contain sections 41-43 that we are indebted for the last five words of sect. 40, so curiously omitted in the oldest and best MSS.; and this is a direct argument against the supposition of any matter having been here lost.

§ 22. The break between sections 43 and 44 may be explained in a totally different manner. In this case, the break indicates a real, not an accidental, gap. I suppose section 43 to have been really the last section of Part ii, and I refer sections 44 and 45 to the Fourth Part of the Treatise, and not to the Second at all. For if we run through the contents of Parts Three and Four (p. 177), we observe that they chiefly involve tables, with reference to one of which we find the words 'upon which table ther folwith a canon,' &c. Now sections 44 and 45 exactly answer the description; they are alternative canons, shewing how certain tables may be used. It happens that Conclusion 40 is particularly dependent upon tables. To supply these was partly the object of Part iv—'the whiche ferthe partie in special shal shewen a table of the verray moeving of the mone from houre to houre, every day and in every signe, after thyn almenak; upon which table ther folwith a canon, suffisant to teche as wel the maner of the wyrking of that same conclusioun, as to knowe in oure orizonte with which degree of the zodiac that the mone ariseth in any latitude; and the arising of any planete after his latitude fro the ecliptik lyne.' The opening words of the same Conclusion are—'Knowe by thyn almenak the degree of the ecliptik of any signe in which that the planete is rekned for to be:' (p. 221). This is easily said; but I suppose that it was not so easy in olden times to know off-hand the exact position of a planet. It must have been shewn by tables, and these tables chiefly considered the 'mene mote,' or average motion of the planets, and that only for periods of years. If you wanted the position of a planet at a given hour on a given day, you had to work it out by figures; the rule for which working was called a 'canon.' This very 'canon' is precisely given at length in sect. 44; and sect. 45 is only another way of doing the same thing, or, in other words, is an alternative canon. When all this is fairly and sufficiently considered, we shall find good grounds for supposing that these sections on the 'mene mote' are perfectly genuine, and that they really belong to Part iv. of the Treatise.

I will only add, that the fact of sections 41a-42b being thus placed after a portion of Part iv. is one more indication that they are spurious.

§ 23. But it may be objected, as Mr. Brae has fairly objected, that Conclusion 40 itself ought to belong to Part iv. So it ought perhaps, if Chaucer had followed out his own plan. But it is clear from its contents that the Prologue to the 'Astrolabie' was written before the commencement of the treatise itself, and not, as prefaces generally are, afterwards. He was pleased with his son's progress. Little Lewis had asked him if he might learn something about an astrolabe. The father at once sent him a small astrolabe by way of reward, constructed for the latitude of Oxford, and having 45 circles of latitude on the flat disc (see Fig. 5) instead of having 90 such circles, as the best instruments had. This, however, was a 'sufficient' astrolabe for the purpose. But he believes the Latin treatises to be too hard for his son's use, and the Conclusions in them to be too numerous. He therefore proposes to select some of the more important Conclusions, and to turn them into English with such modifications as would render them easier for a child to understand, He then lays down a table of contents of his proposed five parts, throughout which he employs the future tense, as 'the firste partie shal reherse,'—'the second partie shal teche,' &c. This use of the future would not alone prove much, but taken in connexion with the context, it becomes very suggestive. However, the most significant phrase is in the last line of the Prologue, which speaks of 'other noteful thinges, yif god wol vouche-sauf & his modur the mayde, mo than I behete,' i.e. other useful things, more than I now promise, if God and the Virgin vouchsafe it. In accordance with his habits of seldom finishing and of deviating from his own plans at pleasure, we have but an imperfect result, not altogether answerable to the table of contents. I therefore agree with Mr. Brae that the 40th Conclusion would have done better for Part iv., though I do not agree with him in rejecting it as spurious. This he was led to do by the badness of the text of the MSS. which he consulted, but we can hardly reject this Conclusion without rejecting the whole Treatise, as it is found in all the oldest copies. By way of illustration, I would point out that this is not the only difficulty, for the Conclusions about astrology ought certainly to have been reserved for Part v. These are Conclusions 36 and 37, which concern the 'equaciouns of houses'; and this is probably why, in three of the MSS. (viz. L., N., and R.), these two conclusions are made to come at the end of the Treatise. There is nothing for it but to accept what we have, and be thankful.

§ 24. If, then, the questions be asked, how much of the Treatise has come down to us, and what was to have been the contents of the missing portion, the account stands thus.

Of Part i. we have the whole.

Of Part ii. we have nearly all, and probably all that ever was written, including Conclusions 1-40 on astronomical matters, and Conclusions 41-43 on the taking of altitudes of terrestrial objects. Possibly Conclusion 46 is to be added to these; but Conclusions 41a-42b are certainly spurious.

Part iii. probably consisted entirely of tables, and some at least of these may very well have been transmitted to little Lewis. Indeed, they may have been prepared by or copied from Nicholas of Lynn and John Somer, before Chaucer took the rest in hand. The tables were to have been (and perhaps were) as follows:—

1. Tables of latitude and longitudes of the stars which were represented on the 'Rete' of the Astrolabe. Specimens of such tables are found in MSS.

2. Tables of declinations of the sun, according to the day of the year.

3. Tables of longitudes of cities and towns.

4. Tables for setting clocks and finding the meridian altitudes (of the sun, probably).

Such tables as these are by no means lost. There are MSS. which contain little else, as e.g. MS. Hh. 6. 8 in the Cambridge University Library. The longitudes of towns are given in MS. Camb. Ii. 3. 3, at fol. 214b. Again, in MS. F. 25, in St. John's College Library, Cambridge, we find tables of fixed stars, tables of latitudes and longitudes of towns, tables of altitudes of the sun at different hours, and many others.

Part iv. was to explain the motions of the heavenly bodies, with their causes. This was probably never written, though there is an allusion to it in Part ii. § 11, l. 12. It was also to contain a table to shew the position of the moon, according to an almanac; and such a table is given in the St. John's MS. above mentioned, and in MS. Camb. Ii. 3. 3, at fol. 143. This was to have been followed by a canon, and an explanation of the working of the Conclusion—'to knowe with which degree of the zodiac that the mone ariseth,' and 'the arising of any planete,' &c. The canon is partly accounted for, as regards the planets at least, by sections 44 and 45, and the 'Conclusion' by section 40.

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&apos;; ii. 4. 36; (p. 192).

§ 25. 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, 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 one of the Latin treatises to which he was very considerably indebted. This is the 'Compositio et Operatio Astrolabie,' by Messahala, of which copies are, I have no doubt, sufficiently numerous. The Cambridge Library has four, viz. Hh. 6. 8, Ii. 1. 13, Ii. 3. 3, and Kk. 1. 1, and there is another copy in St. John's College Library, Cambridge, marked F. 25. The title should be particularly observed; for the treatise is distinctly divisible into two separate parts, viz. the 'Compositio Astrolabii' and the 'Operatio Astrolabii.' The former begins with the words—'Scito quod astrolabium sit nomen Graecum,' and explains how to make an astrolabe, and how to inscribe on it the various necessary lines and circles with sufficient exactness. It is much the longer portion of the treatise, and (in MS. Ii. 3. 3) is illustrated by numerous diagrams, whilst the second part has no such illustrations. But it does not appear that Chaucer made any use of this former part, as his astrolabe had been procured ready-made. The second part of the treatise, or 'Operatio Astrolabii,' begins with the words 'Nomina instrumentorum sunt hec.' This is evidently one of the sources from which Chaucer drew largely. Chaucer's Part i. is almost wholly taken from this, but he has expanded it in several places, with the evident intention of making it more easy to understand. In Part ii. he has taken from it, with more or less exactness, sections 1-3, 5-8, 10, 11, 13-18, 20, 21, 24, 25, 27-31, 33-37, 41 and 42; whilst sections 4, 9, 12, 19, 22, 23, 26, 32, 38-40 and 43 do not appear in it. In other words, Messahala's treatise accounts for thirty-one conclusions out of forty-three, or about two-thirds of the whole. In some places, Chaucer has translated almost word for word, so as to leave no doubt as to his authority. Besides which, I have already remarked that Chaucer's version is directly connected with Messahala by the quotations from the latter which appear in MS. E.; see description of this MS. at p. lix. If it be inquired, whence did Chaucer derive the remaining third of his Second Part, I think it very likely that some of it may be found amongst the varied and voluminous contents of such a MS. as Ii 3. 3, which is a sort of general compendium of astronomical and astrological knowledge. The complete solution of this question I leave to some one with more leisure than myself, being satisfied that to have found the original of Part i. and two-thirds of Part ii. is to have made a good start. It must not be omitted, that the MSS. of Messahala are not all alike; that some copies have propositions which are not in others; and that the order of the Conclusions is not invariable. The chief noteworthy difference between Chaucer's version and the Latin original is in the order of the Conclusions; it is clear that Chaucer not only took what he liked, but rearranged his materials after his own fashion.

§ 26. About the early printed editions of the Astrolabe, I have not much to say. The Editio Princeps of 1532 was clearly derived from some MS. of the second class, and, what between the errors of the scribes and printers, absurdities abound. After a careful examination of the old editions, I came to the conclusion that the less I consulted them the better, and have therefore rather avoided them than sought their assistance. All the editions not only give the conclusions in a wrong order, but (like the MSS. of the second class) absurdly repeat Conclusion I. of Part ii., and reckon the repetition of it as Conclusion III. MSS. of the first class are free from this defect, and may thus be easily known. The only edition worth consulting is that by Mr. A. E. Brae, published quite recently, in 1870. Mr. Brae made much use of MS. I., besides which he consulted the Printed Editions, and MSS. H. and L. See the descriptions of these MSS. above. From this edition I have taken many hints, and I wish to express, very thankfully, my obligations to it. Mr. Brae has brought to bear upon his work much skill and knowledge, and has investigated many points with much patience, minuteness, and critical ability. But I cannot but perceive that he has often expended his labour upon very inferior materials, and has been sometimes misled by the badness of those MSS. to which alone he had access.

Besides his print of Chaucer's Astrolabe, Mr. Brae has reprinted some curious and interesting critical notes of his own, and has added some essays on Chaucer's 'prime,' on 'the Carrenare,' and 'shippes opposteres.' To all that he has done I am much indebted.

§ 27. The works upon, and descriptions of, the astrolabe, are numerous. I have had neither time nor inclination to make researches into the subject; for which reason I here note the names of a few books which may be examined by the curious reader.

In his Universal Lexicon, Zedler explains that astrolabes are of two kinds, 'universal' and 'particular.' He speaks of the astrolabes (1) of Gemma Frisius; see Petri Apiani Cosmographia, per Gemmam Phrysium restituta; (2) of Johan de Rojas, a Spaniard, A.D. 1550; (3) of De la Hire the elder, professor of mathematics at Paris, A.D. 1702; (4) of Johannes Stoflerinus (or Stöffler), A.D. 1510. The last of these varied from the others in adopting a different and more convenient system of projection, viz. that upon the plane of the equator, or one parallel to it, the eye being in the antarctic pole, and the arctic pole being made the centre of the instrument. This projection is the same as that which was used by Ptolemy, and it is adopted in the diagrams which accompany Chaucer's treatise in some of the MSS. It should be observed here that the term 'astrolabe' alone is vague; it was originally a general name for any circular instrument used for observation of the stars; but in the sixteenth and seventeenth centuries it was restricted to the particular kind called the 'Astrolabe Planisphere,' or astrolabe on a flat surface, in which sense alone the word is used throughout this volume. See the English Cyclopaedia, Arts and Sciences, s.v. Astrolabe.

The simplest work is that by Stöffler or Stoflerinus, as he calls himself; see also Gemma Frisius, Metius, Clavius Bambergensis, the Cursus Mathematicus of Dechales, vol. iv. p. 161, Delambre's History of Astronomy, and other works. The plates in Metius are most exquisitely engraved, and on a large scale, and give a better representation of the instrument than any others that I have seen.

One of the MSS., viz. MS. E., refers to an astrolabe belonging to Merton College, Oxford. There is a very nice one, made of brass, and by a Dutch engraver, in the library of King's College, Cambridge. It has several discs or plates, or, as Chaucer calls them, 'tables .' Of this instrument the same library contains a written description, with some account of the problems it will solve, and an investigation of its probable date, by H. Godfray, Esq., of St. John's College.

There is a book entitled 'A verie briefe and most plaine description of Mr. Blagrave his Astrolabe,' &c., by Mr. Blundevill; London, printed by William Stansby. But it turns out to be of little practical assistance, because Blagrave's astrolabe was on a different principle.

§ 28. There is not, however, much need of reference to books to understand what the astrolabe used by Chaucer was like. The instrument may be readily understood from a brief description, and from the Plates in this volume.

The most important part of the 'astrolabe planisphere' consisted of a somewhat heavy circular plate of metal from four to seven inches in diameter, which could be suspended from the thumb by a ring (i. 1), working with such freedom as would allow the instrument to assume a perfectly perpendicular position (i. 2). One side of the plate was perfectly flat, and was called the back. This is represented in Fig. 1. On it was described a number of concentric rings, marked with various divisions, which may be readily understood from the figure. Beginning at the outermost ring, the first two represent the ninety degrees into which each quadrant of a circle can be divided (i. 7). The next two represent the signs of the zodiac, each subdivided into thirty degrees (i. 8). The next two represent the days of the year, and are rather difficult to mark, as the circle has, for this purpose, to be divided into 365¼ equal parts (i. 9). The next three circles shew the names of the months, the number of days in each, and the small divisions which represent each day, which coincide exactly with those representing the days of the year (i. 10). The two innermost rings shew the saints' days, with their Sunday-letters. Thus, above the 21st of December is written 'Thome,' i.e. St. Thomas's day, its Sunday-letter being E; the rest can easily be traced by the tables in a Prayer-book (i. 11). These may be thus briefly recapitulated:—

1 and 2. Circles of degrees of the quadrant and circle.

3 and 4. Circles of the zodiacal signs, with their degrees.

5 and 6. Circles of the days of the year, with their numbers.

7, 8 and 9. Circles of the months, with their days and numbers of the days.

10 and 11. Circles of saints' days, with their Sunday-letters.

Within all these, are the Scales of Umbra Recta and Umbra Versa, in each of which the scale is divided into twelve equal parts, for the convenience of taking and computing altitudes (i. 12). This primitive and loose method of computation has long been superseded by the methods of trigonometry. Besides these circles, there is a perpendicular line, marking the South and North points, and a horizontal line from East to West.

The other side of the plate, called the front, and shewn in Fig. 2, had a thick rim with a wide depression in the middle (i. 3). The rim was marked with three rings or circles, of which the outermost was the Circle of Letters (A to Z) representing the twenty-four hours of the day, and the two innermost the degrees of the quadrants (i. 16). The depressed central portion of the plate was marked only with three circles, the 'Tropicus Cancri,' the 'Æquinoctialis,' and the 'Tropicus Capricorni' (i. 17); and with the cross-lines from North to South, and from East to West (i. 15). But several thin plates or discs of metal were provided, which were of such a size as exactly to drop into the depression spoken of. The principal one of these, called the 'Rete,' is shewn in Fig. 2. It consisted of a circular ring marked with the zodiacal signs, subdivided into degrees, with narrow branching limbs both within and without this ring, having smaller branches or tongues terminating in points, each of which denoted the exact position of some well-known star. The names of these stars, as 'Alhabor,' 'Rigel,' &c., are (some of them) written on the branches (i. 21). The 'Rete' being thus, as it were, a skeleton plate, allows the 'Tropicus Cancri,' &c., marked upon the body of the instrument, to be partially seen below it. Another form of the 'Rete' is shewn in Fig. 9, and other positions of the Rete in Fig. 11 and Fig. 12. But it was more usual to interpose between the 'Rete' and the body of the instrument (called the 'Mother') another thin plate or disc, such as that in Fig. 5, so that portions of this latter plate could be seen beneath the skeleton-form of the 'Rete' (i. 17). These plates are called by Chaucer 'tables,' and sometimes an instrument was provided with several of them, differently marked, for use in places having different latitudes. The one in Fig. 5 is suitable for the latitude of Oxford (nearly). The upper part, above the Horizon Obliquus, is marked with circles of altitude (i. 18), crossed by incomplete arcs of azimuth tending to a common centre, the zenith (i. 19). The lower part of the same plate is marked with arcs denoting the twelve planetary hours (i. 20).

At the back of the astrolabe revolved the 'rule,' made of metal, and fitted with sights, represented in Fig. 3 (i. 13). At the front of it revolved the 'label,' represented in Fig. 6 (i. 22).

All the parts were held together by the central pin (Fig. 4) which passed through the holes in the 'moder,' plates, 'Rete,' rule, and label, and was secured by a little wedge (i. 14), which was sometimes fancifully carved to resemble a horse (Fig. 7).

Another 'table' or disc is shewn in Fig. 14, and was used for ascertaining the twelve astrological houses.

§ 29. I here briefly enumerate such principal uses of the instrument as are mentioned by Chaucer.

The back (Fig. 1) shews at once the degree of the zodiac answering to every day in the year (ii. 1). The altitude of the sun can be taken by the 'Rule,' elevated at the proper angle (ii. 2). If the Rete be properly adjusted to this altitude, we can thus tell the hour of the day (ii. 3). The duration of twilight can be calculated by observing when the sun is 18° below the horizon (ii. 6). Observe the times of sunrise and sundown, and the interval is the 'artificial day' (ii. 7). This day, with the duration of morning and evening twilights added to it, is called the 'vulgar day' (ii. 9). The plate in Fig. 5 shews the planetary hours (ii. 12). The placing of the sun's degree on the South-line gives the sun's meridian altitude (ii. 13), and conversely (ii. 14). The back of the instrument can shew what days in the year are of equal length (ii. 15). The degree of the zodiac which souths with any star can be ascertained by observing two altitudes of the star; but the observations must be made when the star is very near the meridian (ii. 17). If the star be marked on the Rete, the said degree is easily found by use of the Rete (ii. 18). We can also find with what degree of the zodiac the same star rises (ii. 19). The use of the Rete also shews the declination of every degree in the zodiac (ii. 20). We can always tell for what latitude a disc such as that in Fig. 5 is constructed, by properly examining it (ii. 21). The latitude of any place can be found by two observations of the altitude of the Pole-star (ii. 23); or of any circumpolar star (ii. 24); or by observing the sun's meridional altitude (ii. 25). The Rete also tells us the 'ascensions of signs,' or how many degrees of the equinoctial circle pass the meridian with a given sign (ii. 27); as also the 'oblique ascensions' of the same (ii. 28). The astrolabe can also be used to discover (but only in an imperfect and approximate manner) the four cardinal points of the compass (ii. 29). We can also compare the altitude of a planet with that of the sun (ii. 30). We can find in what part of the horizon the sun rises (ii. 31); and in what direction to look for a conjunction of the sun and moon (ii. 32); also near what point of the compass the sun is at any given hour (ii. 33). The moon's observed altitude will shew her longitude (ii. 34). We can tell, from two observations of a planet properly made, whether the planet's movement is direct or retrograde (ii. 35). The disc shewn in Fig. 14 helps to shew the 'equations of houses' (ii. 36). The four cardinal points can be found without an astrolabe, by an experiment properly conducted (ii. 38). The astrolabe can be used to find the degree of the zodiac with which any planet ascends, even when the planet is not situated in the ecliptic (ii. 40).

By the use of the Umbra Recta on the back of the instrument, we can take the altitude of an accessible object by a single observation (ii. 41); or of an inaccessible object by two observations (ii. 43). Or, the height of an inaccessible object may likewise be taken by two observations, by the scale marked Umbra Versa (ii. 42).

The few Conclusions not here referred to are chiefly explanatory, or of minor interest.

§ 30. Several of the Latin MSS. upon the Astrolabe give a list of the stars marked upon the Rete. There is a double list, for example, in MS. Ii. 3. 3, in the Cambridge University Library, fol. 70, back. It is given in the form of two tables; the first mentions forty-nine stars, with the degrees of the zodiac which south along with them, and their declinations from the equinoctial line. The second table mentions some only of the same stars, with their longitudes and latitudes, as referred to the ecliptic.

A list of the principal stars usually marked upon the Rete, as shewn in Fig. 2, is given in the Note to Part i. § 21. 4 (p. 357). Fig. 9 shews another Rete, with many of the same stars, with the addition of Markep ( Argous). Alchimech is the same as Azimech, i.e. Virginis; Cor Leonis is  Leonis; and Alfart is  Hydræ.

§ 31. For a general sketch of Astrology, see the English Cyclopaedia, s.v. Worthless as the science is, it is useful to have a few 'facts' for handy reference. I therefore attempt a synopsis of the chief points of it, drawn from Johannis Hispalensis Isagoge in Astrologiam.

To save space, I give the information in a tabular form, wherein I denote the twelve Signs by A., T., G., C., L., V., Li., S., Sa., Cp., Aq., P.; and the seven Planets, Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, by St., J., Ms., Sn., V., My., Mo. What the table exactly means shall be explained presently.

The first line is to be read thus.

Aries is the mansion (or house) of Mars; the exaltation (or honour) of the Sun, in the 19th degree of the sign; the lord of the Triplicity of Aries with its attendant signs is the Sun by day, Jupiter by night, and Saturn in Common, both by day and night; the first Face of Aries (degrees 1 to 10) is that of Mars; the second Face (degrees 11 to 20) is that of the Sun; the third Face (degrees 21 to 30) is that of Venus. And so on for the rest; noting that Gemini is the Exaltation of the Dragon's Head (D. H.), and Sagittarius that of the Dragon's Tail (D. T.).

The meanings of the words are as follows:—

A Mansion or House appears to be that sign in which the planet is peculiarly at home for some reason or other.

The Exaltation or Honour is that degree of a sign in which the planet named has its greatest power; but the degree was often neglected, and Aries was called the Exaltation of the Sun, simply.

The Fall (Lat. occasus vel detrimentum) of a planet is the sign opposite its mansion. Libra is opposite Aries; therefore Libra is the Fall of Mars.

The Dejection or Depression (Lat. dedecus) of a planet is the sign opposite to that of its exaltation. Libra is opposite Aries; therefore Libra is the Dejection of the Sun. And so on.

A Triplicity is a combination of three signs in the form of a triangle, each 120° apart. Thus Aries, Leo, and Sagittarius form the first triplicity; Taurus, Virgo, Capricorn, the second; Gemini, Libra, Aquarius, the third; Cancer, Scorpio, Pisces, the fourth. Equal divisions of a sign (third-parts, namely) are called Faces. There were also unequal divisions called Terms.

The 'mobill' or movable signs are Aries, Cancer, Libra, Capricorn. The 'fixe' or fixed signs are Taurus, Leo, Scorpio, Aquarius. The 'common' signs are Gemini, Virgo, Sagittarius, Pisces.

The signs Aries, Gemini, Leo, &c. (taking every other sign) are diurnal or masculine. The rest, Taurus, Cancer, &c., are nocturnal or feminine.

The first six signs, Aries to Virgo, are northern or sinister signs. So called because astrologers looked towards the east or ascendent.

The last six, Libra to Pisces, are southern or dexter signs.

The signs Cancer to Sagittarius are western, sovereign, right, or direct signs. Cf. Astrol. ii. 28, and see Fig. 2.

The rest, Capricorn to Gemini, are eastern, obedient, tortuous, or oblique signs.

This is all that a reader is likely to want. For other points, see the authorities.