The challenge of allegory is to identify a second meaning--using the same words. So what will we find in the Canon's Yeoman?
His disclosure is crammed with things: chemicals, utensils, vegetable and animal products. Scholars compare these "poetic" lines to and inventory. The vocabulary is equally unfamiliar whether in Middle or Modern English. Here's a sample:
As boole armonyak, verdegrees, boras,
And sondry vessels maad of erthe and glas,
Oure urynals and oure descensories,
Violes, crosletz, and sublymatories,
Cucurbites and alambikes [also],
. . .
Arsenyk, sal armonyak, and brymstoon;
And herbes koude I telle [also many a one],
As egremoyne, valerian, and lunarie.
This goes on for 38 lines! Alchemy is the accepted subject, but many alternate definitions deal with pigment, book-binding, water-proofing, etc.
Much of the vocabulary serves at cross purposes. The patron saint called upon is "Seint Gile." If not personified, the two words--seint gile--mean holy fraud. "Coles" that feed a fire alternately communicate glue or sizing in book construction. Time, introduced as the French temps, plays a complicated role sometimes merging with tempren (to mix). Mulling over the lines heavy with stuff that produces ink, pigment, fixatives and more, I saw the image of a book.
Seeing this servant as a book, it's no wonder he has so much information to give and such great willingness to inform!
. . . I tell each proportion
Of things which we worked upon.
. . .
I will tell you as I was taught.
He provides early memories of a book being constructed, details of things necessary for the manufacture of paper, vellum and inks. When the presentation suddenly changes from a first person narration to a second person report (regarding a procedure gone awry), this tells of notations being made in the book.
Though a canon is a clergyman, the Yeoman clearly states that the canon he is describing in NOT the Canon that was his original companion. "Canon" also refers to scientific volumes of codified information, principles of calculation, or records of celestial events. Chaucer's Astrolabe includes a "canon" that teaches how to compute information about the zodiac, the moon, and the planets.
The Yeoman's laboring at, and lamenting over, multiplication implies the effort of recording tables as one of his "services." When the Yeoman complains of a false canon, this means faulty information, which causes errors in judgment or calculations. The fourteenth century gained new methods of calculating as Arabic numerals (replacing Roman numerals) came into standard use. Besides greater ease of computing, tables were more readily constructed and interpreted.
The Host's first personal question of the Yeoman asks,
Why art thou so discolored of thy face?
The Yeoman responds,
I am so used in the fire to blow
That it hath changed my color.
What can this mean in regard to a book? A pocket-sized book of Chaucer's day that held information on a particular subject (and would be handy to fan a fire!) was a common personal possession, easily carried from place to place. Because it was so transportable, it was called a vade mecum ("go with me"). This is precisely the role given the Yeoman; he traveled with the Canon.
A vade mecum would be used a great deal, which would cause deterioration of its binding and fading of the print--as if one's eyes were bleary as the Yeoman complains.
And of my work yet bleared is mine eye.
The original red pigment of the cover, with wear, would lose its vibrancy and pale to grey--as the Yeoman indicates,
And where my color was both fresh and red
Now is it wan and of a leaden hue.
To minimize wear on this much-used book, it was provided with a protective sheath.
Now may I wear an hose upon mine head.
The "hose" worn by the Yeoman is the poet's playful way of indicating that protective sheath for a vade mecum.
Chaucer creates two very different double images in the Tales. One is the pair of pilgrim brothers as Gemini. The other is the Canon and his Yeoman as two variations of the term "canon"!