The proverb, "Liars must have good memories," means, of course, that people who tell lies are liable to forget just what tale they have told on any particular occasion, and may easily contradict themselves, and so show that they have been untruthful. It is necessary, then, for such a person, unless he wishes to be found out, to remember exactly what lies he has told. Many proverbs have remained in the English language, not so much for the wisdom they contain as for the way in which they express it. Some are in the form of a rhyme--as, "Birds of a feather flock together," and "East and west, home is best." These are always favourites. Others catch the ear because of their alliteration; that is to say, two or three of their words begin with the same letter. Examples of this are: "Look before you leap." The proverb "A stitch in time saves nine" has something of both these attractions, though it is not exactly a rhyme. Other examples of alliteration in proverbs are: "Delays are dangerous," "Speech is silvern, silence is golden." A few proverbs are witty as well as wise, and these are, perhaps, the best of all, since they do not, as a rule, exasperate the people to whom they are quoted, as many proverbs are apt to do. Usually these witty proverbs are metaphors. CHAPTER XV. SLANG. Every child has some idea of what is meant by "slang," because most schoolboys and schoolgirls have been corrected for using it. By slang we mean words and expressions which are not the ordinary words for the ideas which they express, but which are invented as new names or phrases for these ideas, and are at first known and used only by a few people who use them just among themselves. There are all kinds of slang--slang used by schoolboys and schoolgirls in general, slang used by the pupils of each special school, slang used by soldiers, a different slang used by their officers, and even slang used by members of Parliament. The chief value of slang to the people who use it is that at first, at any rate, it is only understood by the inventors and their friends. The slang of any public school is continually changing, because as soon as the expressions become known and used by other people the inventors begin to invent once more, and get a new set of slang terms. Sometimes a slang word will be used for years by one class of people without becoming common because it describes something of which ordinary people have no experience, and therefore do not mention. The making of slang is really the making of language. Early men must have invented new words just as the slang-makers do to-day. The difference is that there are already words to describe the things which the slang words describe. It may seem curious, then, that people should trouble to find new words. The reason they do so is often that they want to be different from other people, and sometimes because the slang word is much more expressive than the ordinary word.