Logical association depends upon the relation of likeness or difference between several things thought of. Things thus associated may have never come into the mind at the same previous time, nor are they necessarily connected in time and space. One may think of a book, and then proceed by association to think of another book by the same author, or of another author treating of the same subject. Or he may think of a book directly opposed to the first, the relation of distinct difference causing the associated idea. Logical association depends upon _inner relations_, and not upon the outer relations of time and space. This _innerness_ of relation between things not connected in space or time is discovered only by experience and education. The educated man realizes many points of relationship between things that are thought by the uneducated man to be totally unrelated. Wisdom and knowledge consist largely in the recognition of relations between things. ASSOCIATION IN MEMORY. It follows from a consideration of the Law of Association that when one wishes to impress a thing upon the memory he should, as an authority says, "Multiply associations; entangle the fact you wish to remember in a net of as many associations as possible, especially those that are logical." Hence the advice to place your facts in groups and classes in the memory. As Blackie says: "Nothing helps the mind so much as order and classification. Classes are always few, individuals many; to know the class well is to know what is most essential in the character of the individual, and what burdens the memory least to retain." REPETITION IN MEMORY. Another important principle of memory is that the impressions acquire depth and clearness by repetition. Repeat a line of poetry once, and you may remember it; repeat it again, and your chances of remembering it are greatly increased; repeat it a sufficient number of times, and you cannot escape remembering it. The illustration of the phonograph record will help you to understand the reason of this. The rule is: _Constant repetition deepens memory impressions; frequent reviewing and recalling what has been memorized tends to keep the records clear and clean, beside deepening the impression at each review_. GENERAL RULES OF MEMORY. The following general rules will be of service to the student who wishes to develop his memory:-- _Making Impressions._ (1) Bestow attention. (2) Cultivate interest. (3) Manifest perception. (4) Cultivate understanding. (5) Form associations. (6) Repeat and review. _Recalling Impressions._ (1) Endeavor to get hold of the loose end of association, and then unwind your memory ball of yarn. (2) When you recall an impression, send it back with energy to deepen the impression, and attach it to as many new associations as possible. (3) Practice a little memorizing and recalling each day, if only a line of verse. The memory improves by practice, and deteriorates by neglect and disuse.