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

that difference hath him to 12, right so the space be-tween thee and

the two markes hath him to the heyghte of the thing. Ensample: I

set caas thou seest it thorw a poynt of 4; after, at the poynt of 3.

10

Now passeth the nombre of 4 the nombre of 3 be the difference of 1;

and right as this difference 1 hath him-self to 12, right so the mesure

be-tween the two markes hath him to the heyghte of the thing, putting

to the heyghte of thy-self to thyn eye; and thus mayst thou werke

fro 1 to 12.

[42b.] Per umbram versam.