The Practical-theoretical form of education is not limited to the apprentice or to the new employee but is equally valuable to the expert, the oldest employees, and the employer. This fact is taken advantage of most wisely by the National Cash Register Company. This company provides instruction suited to the needs of all its salesmen, whether they are new and inexperienced or whether they are the oldest, most efficient salesmen. By means of letters, books, demonstrations, and conventions the salesmen are constantly provided with educative experiences and are kept from the narrowness and lack of progress so characteristic of men in the commercial life after they have become thoroughly established and relatively efficient in their work. In keeping with this modern tendency to <p 273> supplement practical experience with theoretical interpretation, we find a very pronounced increase in the utilization of all agencies that interpret and enrich the daily toil. Men who are fully employed (_e.g_. journeymen and salesmen) have realized the necessity of some form of theoretical instruction to enable them to profit by their daily practical experience. This fact is almost pathetically demonstrated by the multitudes who are seeking for such instruction through correspondence and evening schools. Every progressive engineer, teacher, physician, and lawyer keeps abreast of the best thought of the day by means of frequent conventions, conferences, books, and periodicals. The experience secured from such agencies is essential to progress; only by such agencies can he learn the latest and most perfect interpretation of the experience of his professional life. Likewise the non-professional man engaged in commerce or industry finds the modern world to be so complex that mere practical experience is no longer adequate to enable him to meet the demands made <p 274> upon him. The theoretical training of his youth (even though it include the college and the technical school) is totally inadequate to interpret for him the new relationships which arise from day to day. He needs a theory that grows out of his practical experience and that enables him to understand and to improve upon his practical work. The most common means for providing him with such experience he finds in his conventions and informal conferences with his peers and in his trade journals and technical books.