By itself this assumption is indeterminate and completely indifferent, but when applied to an object which is internally heterogeneous, that is, constrained by an essentially non uniform quantitative determination, it produces the peculiar reversal contained in that proposition of higher mechanics according to which infinitely small parts of a curve are traversed in equal and infinitely small times in uniform motion, where this is said of a motion in which, in equal finite (that is, concretely existing) parts of time, finite (that is, concretely existing) unequal parts of the curve are traversed that is, is said of a motion which exists concretely as non uniform and is assumed to be such.