or Mnemotecnity (from μνήμη, memory, and τέχνη, art), is the art of improving the memory by artificial means. Its discoverer is said to have been Simonides the poet, who flourished about B.C. 500. The story is, that he had been employed by Scopas, a rich Thessalian nobleman, to compose a song in commemoration of a victory gained by him at the Olympic games. This was sung at a banquet given in honour of the occasion; but Scopas was so displeased that part of it was occupied with the praises of Castor and Pollux, that he said he would pay the poet only one-half of the stipulated reward, as he had received but one-half of the praise, and that he might, if he chose, apply to his friends the Tyndaridae for the remainder. Shortly after this, and while yet at the feast, a message was brought to Simonides that there were two young men at the gate very anxious to speak to him. When he went out he found no one; but while engaged in the search, the house he had just left fell down, killing Scopas and all that were with him. The bodies were so mutilated that they could not be recognised; but Simonides, by calling to mind the place that each had occupied at the feast, was able to distinguish them; and hence his attention was first directed to the important aid afforded to memory by the observation of material objects.

This art was practised and recommended by more than one of the ancients, amongst whom is Cicero, who says—"There can scarcely be any one of so acute a memory that he can retain the order of words and sentences without observing and associating them with material objects; nor, on the other hand, is there any one of so dull a memory as not to receive aid from the use of this plan, . . . . those things being most fixed in the mind which have been given to it and impressed upon it by sense." In modern times the subject of Mnemonics does not seem to have generally received that amount of attention which its importance demands. Various works have indeed been written upon the subject, and various systems advocated, but none of them have met with any great degree of success. This is doubtless chiefly to be accounted for from the fact that the propounders of the various systems have had more in view the exhibiting of mere feats of memory, than the applying of the principles of the art to matters of real value and importance. What Lord Bacon says of the systems of his time is still in a great measure true, that those "now in use are but barren and useless. For immediately to repeat a multitude of names or words once repeated before . . . I esteem . . . no more than rope-dancing, antic postures, and feats of activity; and, indeed, they are nearly the same things, the one being the abuse of the bodily as the other is of the mental powers; and though they may cause admiration, they cannot be highly esteemed."

The value of any system of Mnemonics must necessarily depend upon the extent to which it is based upon the prin- ciples and laws of memory. This term, as it is commonly used, implies both the power of retaining and of recalling whatever may have already been before the mind. These powers vary greatly, not only in different, but even in the same individual,—some having a good retention but a bad recollection, while others have a good recollection but a bad retention. Though thus apparently different in character, they yet seem in reality to be the result of one general principle; a good or a bad retention, as well as a good or a bad recollection, being alike and entirely dependent upon the laws of association. Indeed, so far as retention is concerned, it is held by many philosophers that there are no individual differences,—that whatever has once been the object of consciousness is ever thereafter retained, and that its being or not being recalled depends entirely upon association. In support of this doctrine we have numerous instances of persons recollecting, in the delirium of a fever, things that in ordinary circumstances had long been beyond the power of recall. Thus there have been instances of persons in such a state talking fluently in a language, that of their childhood, which they had long forgotten. In dreams, too, many things are suggested to our minds which we know must be reactivated ideas, even though we cannot recognize them as such.

Memory, then, depends upon what are by philosophers termed the laws of mental association, suggestion, or reproduction. The great law of association, and that to which probably all the others may be referred, is that of contiguity. Ideas that have been in the mind together, or in close succession, ever after manifest a tendency to recall or reproduce each other. As a general rule, we find this tendency most marked, as indeed was to be expected, in persons with few ideas among the ignorant and uneducated. Shakespeare's Mrs Quickly is an admirable instance of this, as she narrates with amazing minuteness the various incidents that happened at the time when Sir John Falstaff had made her a promise of marriage. Where, however, the mind has been actively at work, and has stored up a great number of ideas, those that have been frequently before it have become associated in a variety of ways with numerous other ideas. Such then have the power of suggesting, not only ideas that may have been associated with them at any particular time, but also those that may have been connected with them at various times. Were in such cases every idea to bring before the mind all with which it had at any time been connected, the result would be endless confusion. Instead, therefore, of a host of ideas, we find that generally only one or a few rise before consciousness. That some rather than others are selected and brought before the mind depends upon a variety of circumstances,—such as their affinity to immediately preceding ideas or to the general habits of thought of the individual, their recency or abstractedness from other ideas, or their affinity to the suggesting idea, arising from the frequency or length of time they may have been associated with it.

An idea, however, may give rise to other ideas, with which it had never previously been associated. Thus, Hannibal may immediately suggest Napoleon, though they may have never been previously together in the mind. This is done by means of a third idea common to both: among the various ideas that have been associated in the mind with Hannibal, one is that he crossed the Alps with an armed force; but this latter idea has been also associated in the mind at another time with Napoleon, and hence he is immediately suggested. The common idea is here evident; but frequently it does not come before consciousness, though in every case its influence may be traced. This is what is called the law of similarity, though in reality it seems to be merely a modification of that of contiguity,—the one idea suggesting the other, not directly, but by means of a third idea common to both. To this same principle of contiguity, we think, may also be referred that tendency of the mind to proceed from one idea to its contrary,—as from virtue to vice, from light to darkness, from riches to poverty,—there being in every such case an intermediate idea common to both, of which the one is an abundance and the other a deficiency. It is this principle of association by similarity that we find to predominate in men of genius, as poets, artists, philosophers, and others. It was this that led Sir Isaac Newton to see the one principle of attraction governing alike the falling of an apple and the revolution of a world. Though depending chiefly on natural endowment, it is also to a great degree capable of cultivation.

Another principle of association is that of a part suggesting its whole, or a whole one or more of its parts. Most of our ideas are made up of a number of others. The paper I write upon is, in my mind, made up of ideas of form, colour, smoothness, &c. The mind has the power of analyzing and reducing such an idea to its component parts, so that it becomes merely a number of associated ideas. Any one of these may, in accordance with the ordinary principles of reproduction, suggest the whole idea, or the whole idea may suggest one or more of its parts. Paper may immediately suggest to the mind whiteness, and this whiteness may suggest another, or a number of other things, of which it is likewise a property. In like manner, a word may be resolved into its component parts or syllables, any one of which tends to suggest other words of which it forms a part. Thus, one word may suggest another word or words having the same initial or terminal syllables; and hence the rhythmical terminations of the lines in poetry make it much more readily remembered than prose, and the alliteration so frequent in proverbs renders them pleasing to the memory and easy of recall. The principles of mental association are well illustrated by Coleridge in the following passage:—"Seeing a mackerel, it may happen that I immediately think of gooseberries, because I at the same time ate mackerel with gooseberries as the sauce. The first syllable of the latter word being that which had co-existed with the image of the bird so called, I may then think of a goose. In the next moment the image of a swan may arise before me, though I had never seen the two birds together. In the first two instances, I am conscious that their co-existence in time was the circumstance that enabled me to recollect them; and equally conscious am I that the latter was recalled to me by the joint operation of likeness and contrast. So it is with cause and effect; so too with order."

It follows naturally, as a principle of contiguity, that, as a general rule, the closer ideas are brought together in the mind, the more strongly will they be associated, and the greater will be their power of reproducing each other. When an interval takes place between ideas brought before consciousness for the purpose of being associated together, there is ever a tendency of irrelevant ideas to spring up in the mind and interfere with their adhesion. This is especially marked when our circumstances are such as to readily suggest ideas to our mind apart from those we wish to impress upon it. Hence the importance to memory of sound health and a mind free from anxieties. Sensations exercise an important influence in the direction of our thoughts, and in giving rise to new trains of ideas; and indeed it seems highly probable that there are conditions of body, even beyond the pale of consciousness, that exert an important influence in this respect.

Memory, probably more than any of the other faculties of the mind, is dependent on the physical condition of the body. We may smile as we read in old works on Mnemonics of "plasters to prevent a decay of memory," "a pouder for the memory," or "a perfumed apple for comforting the brain and memory;" but these all indicate a belief in the dependence of memory upon the physical condition of the body; and we find in the present day so high a medical authority as Sir Benjamin Brodie supporting the same opinion when he says, "It is possible that by accurate observation the proper means may be discovered of preserving that temperament of the brain which is favourable to memory, and of remedying the disorders of that temperament."

Some ideas are much more easily retained and recalled than others,—those presented to us by the senses occupying in this respect the chief place. The mind is first awakened to consciousness by sensations, and these are ever the most easy of retention or reproduction. Of all the senses, that of sight is the one that furnishes the mind with most ideas, and these are always the most vividly and lastingly impressed upon it. In cases of loss of memory we frequently find that, after all other sensational ideas have been lost, those of sight may still be retained. Thus, a sentence when spoken may convey no idea to the mind, while the same when written may be readily understood; and one may be able to write what, from mere obliviousness of the sound, he is unable to speak. Most persons, too, may have experienced, when in doubt as to the correct spelling of a word, that they have frequently been put right by recalling to the mind the appearance of the word, or by writing it down. When two or more of the senses are employed in impressing a thing upon the mind, the advantage is greater than if only one were employed. Every schoolboy knows that he learns his lesson much more quickly by repeating it aloud, for in this case he has both the ear and the eye to assist him; and next to the eye the ear is, as an aid to memory, the most valuable of the senses.

We have been thus minute in explaining the principles of memory, because, as already said, it is only in accordance with these that memory can be judiciously improved; and further, because we believe that no one system of Mnemonics can be equally beneficial in every case. Mnemonics is the art of associating in the mind things difficult with things that are easily remembered, so that the former may be retained and recollected from being associated with the latter. Memory, however, varies greatly in different individuals, some manifesting the greatest facility in remembering places, others events, others names, and so on, according to the species of memory that each may have received from nature, or acquired by previous education. In each particular case it is of importance to know where the strongest points of memory lie, and to employ these in the assistance of the weaker.

One great principle of mental association is to bring together as nearly as possible in the mind ideas that we wish to connect, as by this means we guard against irrelevant ideas intervening that would injuriously affect their adhesion. It is upon this principle that what is called the Hamiltonian system of teaching languages is constructed,—that, namely, of bringing the foreign word and the English equivalent into the nearest possible proximity.

Another important principle that, from the foregoing considerations, we arrive at, is that of associating an abstract idea that we wish to remember with a sensational. Most persons must have observed, that in passing along a road which they had formerly travelled in the company of a friend, the particulars of a conversation in which they were then engaged are frequently suggested by the objects they meet with. They recollect that in such a place a particular subject was started, and as they pass the various houses, plantations, rivers, &c., on the way, the parts of the subject under discussion when these were last seen are immediately suggested to the mind. The same result will be obtained, though less perfectly, by merely bringing the various objects before the mind in imagination—the ideas associated with each will spring up. We may in this way connect ideas that we wish to remember with the public buildings of a town, the houses of a street, or the furniture of a room, and by going over these objects in reality or in imagination, the ideas formerly associated with them will spring up. This is the system of Mnemonics as recommended and practised by Cicero, Quintilian, and others.

Another principle, even more important than the last, because it belongs to a higher and more advanced state of mind, is that of associating what we wish to remember with ideas already in the mind; and according to the familiarity of these ideas will be their value as a means of reproduction. As the mind enlarges and becomes stocked with ideas, we find that suggestion comes to depend more and more upon what are commonly called the laws of similarity or contrast. In reading the account of a battle, for instance, one will best remember it by associating it with another already in his mind, and noting the points of resemblance or contrast. It is the same with other branches of history, with biography, or with more abstract subjects. Hence the great importance of exercise to the memory, by which it is not only strengthened, but by which stores of materials are laid up with which to associate new acquirements. A law prevails in the mental world similar to that of chemical attraction in the material,—a law by which ideas with certain affinities are attracted to each other and all others repelled.

It may be considered necessary, before concluding the present article, to say something of the means commonly adopted by Mnemonicians for performing their great feats of memory. For this purpose a number of rooms are selected, the walls and floor of which are each divided in imagination into 9 equal parts or squares, 3 in a row. On the front wall (that opposite the entrance) of the first room are the units, on the right hand wall the tens, the left hand the twenties, the fourth wall the thirties, and the floor the forties. Nos. 0, 10, 20, and 30 each find a place on the roof immediately above their respective walls, while 40 is placed in the centre of the roof. One room will thus supply 49 places, and with 10 rooms we may have 500 places, all save one. Having fixed these in the mind so that the exact position of each place may be readily ascertained it is then necessary to associate with each of them a certain familiar object, so that, on the object being suggested, its place may be recalled; or when the place is before the mind, its object may immediately spring up. When this has been done thoroughly, the objects can be run over in any order from beginning to end, from end to beginning, or the place of any one can at once be given. It will also facilitate reference if the objects are arranged according to a certain plan. Each room may be devoted to one class of objects, the subdivisions of which may occupy the various places on the walls and floor, on the same principle as a librarian arranges the books of his library, or a naturalist the objects in his museum. All that is further necessary is to associate the subjects that we wish to remember with the objects in the various places, by which means they are readily remembered, and can be gone over in any order. In this way some are able to repeat in any order several hundred disconnected, or even unmeaning, words or ideas, after having once heard them.

To remember dates or sums, letters are substituted for the figures, and formed into words. Thus:

\[ \begin{array}{cccccccc} t, n, m, r, l, d, c & g, q, b, k & e, w, p, f & s, z \\ 1, 2, 3, 4, 5, 6, 7, 8, 9, 0. \end{array} \]

The vowels are of no value, but are merely introduced between the consonants to form words. In this way tin, tone, ten, tum, &c., stand for 12; tins, tens, &c., for 120; and tabbed for 1856. This last branch of Mnemonics, which we cannot enter upon at greater length, will be found fully treated of in Dr Grey's Memoria Technica, and exemplified in history, geography, astronomy, &c.