And in every case it is some underlying thing with a distinct nature of its own, eg in the scale a quarter tone, in magnitude a finger or a foot or something of the sort, in rhythms a beat or a syllable; and similarly in weight it is a definite weight; and in the same way in all cases, in qualities a quality, in quantities a quantity (and the measure is indivisible, in the former case in kind, and in the latter to the sense);