Chaucer's Works, Volume 3 — The House of Fame; The Legend of Good Women; The Treatise on the Astrolabe; The Sources of the Canterbury Tales

by Geoffrey Chaucer

for the more declaracioun, lo here thy figure.

[12.] Next the forseide Cercle of the Abc., under the cros-lyne,

is marked the scale, in maner of two squyres, or elles in manere

of laddres, that serveth by hise 12 poyntes and his devisiouns of

ful many a subtil conclusioun. Of this forseide scale, fro the

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croos-lyne un-to the verre angle, is cleped umbra versa, and the

nether partie is cleped the umbra recta, or elles umbra extensa.

And for the more declaracioun, lo here the figure.

[13.] Thanne hastow a brood Rewle, that hath on either ende a