In the introduction to this Variorum edition of Geoffrey Chaucer's Treatise on the Astrolabe Sigmund Eisner, the editor, remarks on "the dearth of serious commentary" on the treatise. His edition will certainly stimulate such commentary by providing a secure basis for it in the form of full textual data, generous explanatory material, including numerous illustrative figures, and expert guidance through issues relating to the instrument, the treatise, star-study in general, and the bearing of these on Chaucer's life and poetry.
The edition presents for the first time a complete record of substantive manuscript variants. These are conveniently located just below the edited text, so that one can easily spot areas of significant diversity among manuscript readings. In ll.24f of the Prologue, for example, variation in the verb-forms suffice/suffisith calls attention to grammatical anomaly at a point in the text where Chaucer seems to be referring to the "full light reules" of English grammar. Conversely, one can readily consult manuscript attestation for readings that, on non-textual grounds, have seemed questionable. At Astrolabe I.12, for example, Chaucer (or someone) seems to have transposed the terms umbra recta and umbra versa. One modern edition of the treatise (John H. Fisher's, in The Complete Poetry and Prose of Geoffrey Chaucer) says that the transposition occurs in nearly all manuscripts, and another (in the Riverside Chaucer) says that it occurs in all of them. Eisner's full record of variants clears up the question: the transposition occurs in all manuscripts except one sixteenth-century manuscript edition.
The manuscripts in which the Astrolabe occurs are fully described in the editor's Introduction, and their relations of affiliation and dependence are established as clearly as can reasonably be expected. We are also told, in most cases, what other works are bound with the Astrolabe (and when) in the same codices. Also in the Introduction is a survey of such textual commentary as has thus far been produced, from which it appears that current thinking in terms of "hypertext," "versioning," and textual "mouvance" has not yet penetrated to the Astrolabe.
Eisner is the first editor since W. W. Skeat and R. T. Gunther to print the so-called "Supplementary Conclusions" (those following the conclusion numbered II.40 in modern editions). They are on the whole, he says, "probably not Chaucer's work" (99), although "something of the added portions may have been written by Chaucer" (40). He cites Skeat's remark that the fragmentary nature of these conclusions shows Chaucer to have been "a fragmentary worker" in the Astrolabe as in the Canterbury Tales, but taken as a whole, textual studies leave questions of the authenticity of these parts to stand as they did in 1940, when P. Pintelon wrote that "the exact point where Chaucer left off his work is still an unsolved little problem" (Pintelon, ed., Chaucer's "Treatise on the Astrolabe" [Antwerp, 1940], 57). It is good, therefore, to have the Supplementary Conclusions presented here along with Eisner's textual and explanatory notes.
The numerous drawings provided by the editor, better adapted to their illustrative purposes than any set provided in surviving manuscripts, are very helpful. Having them available as one reads Chaucer's text is almost like having an astrolabe in hand and someone alongside to point out the various parts and functions of the instrument. They are, as the editor says, the result of careful examination of an actual astrolabe (called the "Painswick astrolabe") that "according to known location and chronology could have been handled by Chaucer" (9). It is therefore especially unfortunate that the two photographs of it purporting to show the front and back sides (frontispiece and p. 102) actually both show the front.
The explanatory notes, placed just below the textual notes, well fulfill their basic function of explaining how the astrolabe itself works, especially in connection with the second part of the treatise, the part in which operations performed with the instrument are described. The notes for each section (or "conclusion") begin with Eisner's brief description of the operation in question, based on his own experience with the instrument. (Skeat had done something similar in his edition, but Eisner's descriptions are clearer and better informed.) In addition, marginalia from the manuscripts, sometimes quite extensive, are quoted in the notes. They can give interesting hints at the intellectual contexts in which the treatise was read, as when marginal glosses, accurate or inaccurate, of technical terms such as nadir (194) show how well or ill the term and concept were understood. References to other writings suggest readers' backgrounds, as when information in Astrolabe II.6, on crepuscular periods experienced at a given latitude, is said in a Latin note in two manuscripts to be paralleled in a treatise on the instrument called the quadrant ("in tractu quadrantis prefacii" -- unidentified in the note but almost certainly the treatise on the "new quadrant" by Profatius Judaeus, called in one medieval treatise "tractatus novi quadrantis Prefatii Iudaei").
An additional function of the explanatory notes, supported by the Introduction's survey of critical commentary, is to locate the Astrolabe in relation to Chaucer's life and works. In connection with the life, to take one obvious example, the Astrolabe's opening address to "Lyte Lowys my sone" is explored for biographical relevance, including possible relevance to the episode involving Cecilia de Champaigne and her release of Chaucer from charges "de raptu meo." With regard to the works, the frequent references to the stars in Chaucer's poetry are cited whenever the Astrolabe seems to provide a gloss on them, as when in II.4 the discussion of horoscopes is referred to all those places in the poetry where the concept is (or is thought by commentators to be) a factor. The whole question of Chaucer's attitude toward and poetic use of astrology is thoroughly inspected, though in this matter as in others Eisner is properly intent on providing reliable information rather than on breaking new interpretive or theoretical ground. He is, for example, respectful of the work done on Chaucer by J. D. North in his capacity as a historian of science -- calling his work "monumental" (31) -- but non-committal on North's tendency to read much of Chaucer's poetry as a secret allegory of the stars. Eisner is likewise even-handed (or reticent) on issues such as Chaucer's status as a technical writer, pedagogue, prose stylist, and translator.
Eisner has over the years demonstrated that he is an accomplished editor, astrolabist, and Chaucerian. His edition of the Astrolabe is distinguished by expertise in all three capacities.