How then, you may ask, is a weak memory to be strengthened, or a fairly good memory to be cultivated into a better one? The answer is, by constant practice, and for this the vocation of a librarian furnishes far more opportunities than any other. At the basis of this practice of the memory, lies the habit of attention. All memory depends upon the strength or vividness of the impression made upon the mind, by the object, the name, the word, the date, which is sought to be remembered. And this, in turn, depends on the degree of attention with which it was first regarded. If the attention was so fixed that a clear mental image was formed, there will be no difficulty in remembering it again. If, on the other hand, you were inattentive, or listless, or pre-occupied with other thoughts, when you encountered the object, your impression of it would be hazy and indistinct, and no effort of memory would be likely to recall it. Attention has been defined as the fixing of the mind intently upon one particular object, to the exclusion for a time, of all other objects soliciting notice. It is essential to those who would have a good memory, to cultivate assiduously the habit of concentration of thought. As the scattering shot hits no mark, so the scattering and random thoughts that sweep through an unoccupied brain lead to no memorable result, simply from want of attention or of fixation upon some one mental vision or idea. With your attention fastened upon any subject or object, you see it more clearly, and it impresses itself more vividly in the memory, as a natural consequence. Not only so, but its related objects or ideas are brought up by the principle of association, and they too make a deeper impression and are more closely remembered. In fact, one thing carefully observed and memorized, leads almost insensibly to another that is related to it, and thus the faculty of association is strengthened, the memory is stimulated, and the seeds of knowledge are deeply planted in that complex organism which we call the mind. This power of attention, of keeping an object or a subject steadily in view until it is absorbed or mastered, is held by some to be the most distinctive element in genius. Most people have not this habit of concentration of the mind, but allow it to wander aimlessly on, flitting from subject to subject, without mastering any; but then, most people are not geniuses. The habit to be cultivated is that of thinking persistently of only one thing at a time, sternly preventing the attention from wandering.