In all these cases, there is an act of pure memory, a direct and positive power of summoning into the mind its past experiences, such as can only take place where, either by natural gift or by special training, the memory as a faculty of the mind is in a high state of vigor. But there are other cases, in which a man is enabled to recall a great number of particular facts by a species of artifice or trick, which does not imply any special mental power, and the study of which does not tend, in any marked degree, to develop such power. More than thirty years ago, the late Professor Dod, of Princeton College, in lecturing to a class on the subject of light, was explaining the solar spectrum, and after exhibiting the solar ray, divided into its seven primary colors, violet, indigo, blue, green, yellow, orange, and red, said, "If you will form a mnemonic word of the first letters of each of these words, you will be able, without further effort, to remember the order of the prismatic colors the rest of your lives," and he accordingly wrote upon the board and pronounced the uncouth and almost unpronounceable word, _Vibgyor_, which probably not one of us has ever forgotten. An ingenious Frenchman some years ago traversed the country and collected large audiences by his exhibitions of skill in this species of artifice, and by undertaking to initiate his hearers in the method of remembering prodigious numbers of historical facts by means of such artificial contrivances. Mnemotechny, the name which he gave to his invention, is merely a trick of the memory. It is a means of remembering a particular set of facts or things by the aid of contrivances purely artificial and arbitrary. Its possession does not imply, and its cultivation does not produce, real mnemonic power. It undoubtedly has its uses. But it is rather wealth gained by a lottery ticket than a wealth-producing power acquired by wise habits of business. In teaching the young, it is well not to neglect either of these principles. We should give our children from time to time ingenious and interesting contrivances for remembering important facts. These contrivances, if judicious in plan and execution, will be great helps to them. We may in this way bridge over the difficulty of remembering many of the important facts and dates in history.