As attention is considered an exertion of the will on the organs of sense and faculties of the mind, it may be allowable to remark on the nature and meaning of the term. It was evidently imposed under a prevailing hypothesis, that the mind possessed a power of stretching or extending itself to the objects of its perception, or to the subjects of reflection; it is therefore a figurative term. Indeed something of this nature actually takes place in the organ:--in minute examinations by the eye, we actually strain and stretch its muscles, and feel the fatigue which results from over-exertion:--when we listen, the neck is stretched forward, and such position enables us to collect those vibrations of sound, that would be otherwise inaudible. We are not unaccustomed to describe the higher and more felicitous productions of intellect, as a vigorous grasp of the mental powers, or as a noble stretch of thought: but to infer that the mind itself was capable of being extended, would be to invest it directly with the properties of substance, and at once plunge us into the grossest materialism. The perfection of this voluntary direction, or, as it has been termed, faculty of attention, consists in intensity and duration. Of the former there can be no admeasurement, excepting by its effect, which is recollection: its duration can be well ascertained. The faculty of attention in the human mind may be exerted in two ways; first, by the organs of sense to the objects of perception; and, secondly, by the mind to the subjects of its recollection; and this latter exercise of attention, as will be hereafter explained, seems to be in a very great degree peculiar to man, and to be nearly wanting in animals. According to the nature and constitution of the human mind, the effective duration of the attention seems to be very limited: if the eye be steadily directed to any particular object, after a few seconds, it will be found to wander; and if the mind be exerted on the subjects of its recollection, there is very soon perceived an interruption, from the intrusion of irrelevant thoughts. The effective duration of the attention will much depend on the superior capacity, nature, or constitution of the intellect itself; but still more on the manner in which these habits of attention are exercised; for, by proper cultivation, its duration may be considerably protracted. As a proof of the limited endurance of the faculty of attention in ordinary minds, allow the following experiment to be made.