Theory of ratios; the nature of gravity and levity
Boethian proportions on 38v; gravity and levity as accidental powers on 37r
The verso (38v) sets out the classical theory of numerical proportion — the species of "greater inequality" (multiple, superparticular, superpartient) with worked examples such as sesquialtera (3:2) and double-sesquialtera (5:2), together with their tabulated ratios. The recto (37r) turns to natural philosophy, defining gravity and levity as "accidental powers" created by motion and infused into a body displaced from its natural place, and naming gravity, force, motion and percussion as the four accidental powers behind all mortal works. Three small lettered figures accompany the discussion of gravity on 37r.
On this page
The species of numerical proportion
Greater inequality is divided into simple (multiple, superparticular, superpartient) and composite kinds. The multiple contains the smaller term an exact number of times (double, triple, quadruple); the superparticular adds one aliquot part (sesquialtera 3:2, sesquitertia 4:3, sesquiquarta, sesquiquinta); the superpartient adds a non-aliquot part made of aliquot parts, as 5 to 3.
The four accidental powers
Gravity, force, material motion and percussion are named the four accidental powers by which all the evident works of mortals have their being and their death. Gravity is defined as an accidental power created by motion and infused into one element drawn or pushed into another, living only as long as that element labours to return home.
Gravity and levity as transmuted contraries
Invisible gravity is an accidental power created by motion and infused into bodies standing outside their natural place. Gravity and levity are two elements transmuted one into the other, so alike in every office except in the motions of their creation and privation that they are almost to be named one and the same.
