On the Sublime and Beautiful/Part II/Chapter 9

ANOTHER source of the sublime is infinity; if it does not rather belong to the last. Infinity has a tendency to fill the mind with that sort of delightful horror, which is the most genuine effect and truest test of the sublime. There are scarce any things which can become the objects of our senses, that are really and in their own nature infinite. But the eye not being able to perceive the bounds of many things, they seem to be infinite, and they produce the same effects as if they were really so. We are deceived in the like manner, if the parts of some large object are so continued to any indefinite number, that the imagination meets no check which may hinder its extending them at pleasure.

Whenever we repeat any idea frequently, the mind, by a sort of mechanism, repeats it long after the first cause has ceased to operate. After whirling about, when we sit down, the objects about us still seem to whirl. After a long succession of noises, as the fall of waters, or the beating of forge-hammers, the hammers beat and the water roars in the imagination long after the first sounds have ceased to affect it; and they die away at last by gradations which are scarcely perceptible. If you hold up a straight pole, with your eye to one end, it will seem extended to a length almost incredible. Place a number of uniform and equi-distant marks on this pole, they will cause the same deception, and seem multiplied without end. The senses, strongly affected in some one manner, cannot quickly change their tenor, or adapt themselves to other things; but they continue in their old channel until the strength of the first mover decays. This is the reason of an appearance very frequent in madmen; that they remain whole days and nights, sometimes whole years, in the constant repetition of some remark, some complaint, or song; which having struck powerfully on their disordered imagination in the beginning of their phrensy, every repetition reinforces it with new strength; and the hurry of their spirits, unrestrained by the curb of reason, continues it to the end of their lives.