To be more specific.--As regards any particular thing which you wish to remember: 1. Grasp it fully, clearly, definitely in the mind; be sure you have it exactly--_it_, and not something like it or something about it. 2. Connect it with other things that are known; suffer it to link itself with other ideas and impressions already in the mind, that you may have something to recall it by. 3. Frequently revert to it, until you are sure that it has become a permanent possession, and one which you can at any time recall by any one of numerous connecting links. In this way you secure the two conditions already specified as essential, viz., frequency of coëxistence, and vividness of conception. _Systems of artificial Memory._--A thing is recalled by the suggestion of any _coëxisting_ thought or feeling. Observing this, ingenious men have availed themselves of the principle of association to construct various mechanical or artificial systems of memory, usually termed _mnemonics_. The principle of the construction is this: should you see an elm or an oak-tree, or hear a particular tune whistled, at the same time that you were going through a demonstration in Euclid, you would be likely to think of the tree or the tune whenever next you had occasion to repeat that demonstration. The sight of the diagram would recall the associated object. They _stand together_ in your mind afterward. This we have already found to be the groundwork and chief element of all association of ideas and feelings, viz., _prior coëxistence_ in the mind. Suppose, now, you wish to fix in the mind the list of English kings. Make out a corresponding list of simple figures, or images of objects, giving each its invariable place in relation to the series: No. 1. a pump; No. 2. a goose, etc., till you reach a sufficient number, say a hundred. These are committed to memory, fixed indelibly in the mind. You then associate with those figures your English kings; Charles I. stands by the pump; Charles II. pursues the goose; James hugs the bear, and so on. These things thus once firmly linked together, remain afterward associated, and the figure serves at once to recall the associate monarch and to fix his place in the series. The same series of figures, of course, will serve for any number of different series of events, personages, etc., which are to be remembered.