It is usually a good idea to arrange what might be called a “unit” program that will include everything that it is desirable for a given visitor or group of visitors to do, see, and hear in order to fully understand and enjoy the message. This unit program has an important place in the arrangement of itinerary, schedule, and the arrangements made for the attendance. For example, if the unit program lasts an hour we have a means of deciding the number of times it needs to be repeated in order to reach the desired number of visitors. If it lasts two or three hours we are likely to find that in our advance work we will need to make a greater effort to attract a carefully selected audience, since the longer the program in most cases the fewer the people who could enjoy it even once. The suggestions below have to do with some of the factors to take into account in selecting and combining features of this unit program. Features intended wholly or mainly as attractions, such as music, or dramatic or comic films, should not be placed in competition with educational features for getting attention or holding interest. They may be said to compete when they distract attention from the main topic or take up an undue share of the time of visitors, or are so much more popular in form than the educational topics as to be more talked about and remembered afterward. The program should be arranged so that the one idea or set of facts which it is the purpose of the tour to deliver holds the center of the stage at all times, and so that it commands attention whether it takes the form of a talk or exhibit, or both. As has already been said, the main idea should not be overshadowed or lost sight of through the rivalry of other attractions. Finally, so that there may be no doubt that it is understood and remembered, the main idea should be repeated in different forms, in talks, demonstrations, exhibits, and printed matter. If the visitor is obliged to stand during all or the greater part of the time he is not likely to give more than an hour of interested attention to talks and displays. Many will give much less. The actual period that the average visitors will remain under certain conditions is soon learned by experimenting, and each feature should be timed so that a satisfactory presentation of the subject can be assured for the majority of them.