impression but from the last; and it can never of itself resume a dissimilar impression: besides every variation of the object is a rest and relaxation to the organs of sight; and these reliefs prevent that powerful emotion so necessary to produce the sublime. To produce therefore a perfect grandeur in such things as we have been mentioning, there should be a perfect simplicity, an absolute uniformity in disposition, shape, and coloring. Upon this principle of succession and uniformity it may be asked, why a long bare wall should not be a more sublime object than a colonnade; since the succession is no way interrupted; since the eye meets no check; since nothing more uniform can be conceived? A long bare wall is certainly not so grand an object as a colonnade of the same length and height. It is not altogether difficult to account for this difference. When we look at a naked wall, from the evenness of the object, the eye runs along its whole space, and arrives quickly at its termination; the eye meets nothing which may interrupt its progress; but then it meets nothing which may detain it a proper time to produce a very great and lasting effect. The view of a bare wall, if it be of a great height and length, is undoubtedly grand; but this is only _one_ idea, and not a _repetition_ of _similar_ ideas: it is therefore great, not so much upon the principle of _infinity_, as upon that of _vastness_. But we are not so powerfully affected with any one impulse, unless it be one of a prodigious force indeed, as we are with a succession of similar impulses; because the nerves of the sensory do not (if I may use the expression) acquire a habit of repeating the same feeling in such a manner as to continue it longer than its cause is in action; besides, all the effects which I have attributed to expectation and surprise in Sect. 11, can have no place in a bare wall. SECTION XIV. LOCKE'S OPINION CONCERNING DARKNESS CONSIDERED.