We observe that superfluous energy rushes out along customary or habitual lines of activity, and so with perfect ease and economy. Activity which is easy and free is in itself pleasant, and this pleasantness in sensing and derived psychosis is æsthetic feeling. Where sensing is mere escape valve of force, though facility is absolute, there is, as just pointed out, no æsthetic quality, the whole tending to the merely mechanical. Owing to the fact that in nature curved lines predominate and so ocular adjustment is to them, my eye follows a curved line easier than a straight one, hence when spontaneous energy outflows in sensing activity of least resistance it will be toward curves. But spontaneous activity of this kind is, as we have explained, not æsthetic. The law of economy in a vent is, greatest force, least effect, the contrary of the usual formula for economy which is, least force, greatest effect. Where energy is expensive the latter rule is to be applied. Thus in directed and effortful sensing activity economy means the ratio of efficiency, the ratio of the amount of painful effort to desired result. But this is merely a saving of pain and not a real pleasure psychosis. When I, in using a microscope see clearly with less and less effort the objects of my study, I may take pleasure in the economical and facile accomplishment, but this pleasure is one of satisfaction in power and skill, and so not at all æsthetic. Again, a dyer has great skill and easy appreciation with respect to colour, but the æsthetic side of colour is not thereby specially felt by him. Mere habitual and easy colour sensitiveness is not then thereby æsthetic. We must, indeed, sense a colour before we can feel its beauty, but the feeling of beauty is not directly involved in any stage of the sensing evolution from the earliest and most painful effort with bare appreciation to the spontaneous and effortless sensing at the moment of great surplus of sensing energy.