In nearly every walk of life are to be found persons with memories wonderfully developed along the lines of their particular occupation. Librarians possess this faculty to an unusual degree. Skilled workers in the finer lines of manufacture also manifest a wonderful memory for the tiny parts of the manufactured article, etc. Bank officers have a wonderful memory for names and faces. Some lawyers are able to recall cases quoted in the authorities, years after they have read them. Perhaps the most common, and yet the most remarkable, instances of memorizing in one's daily work is to be found in the cases of the theatrical profession. In some cases members of stock companies must not only be able to repeat the lines of the play they are engaged in acting at the time, but also the one that they are rehearsing for the following week, and possibly the one for the second week. And in repertoire companies the actors are required to be "letter-perfect" in a dozen or more plays--surely a wonderful feat, and yet one so common that no notice is given to it. In some of the celebrated cases, the degree of recollection manifested is undoubtedly abnormal, but in the majority of the cases it may be seen that the result has been obtained only by the use of natural methods and persistent exercise. That wonderful memories may be acquired by anyone who will devote to the task patience, time and work, is a fact generally acknowledged by all students of the subject. It is not a _gift_, but something to be won by effort and work along scientific lines. CHAPTER IV. MEMORY SYSTEMS.