There is little opportunity to get attention for detailed or complex displays, no matter how attractive and interesting they may be. The following is taken from a description of a mechanical device shown on a train through which visitors were always moving rapidly because there was a long waiting line: “A model block-signal system about 25 feet in length, illustrating the protection provided by a clock-signal system was in full operation. This model had two sidings and was designed particularly to show single-track operation. Intermediate signals were shown between the clock signals by means of lights.” The information that this model conveyed illustrates very well the kind that is too complicated to be understood without a careful examination and some explanation by an attendant. You must, therefore, in planning the form as in planning the content of your exhibit, keep your eye steadily on the picture of the Smiths and Browns at the train as it stands on the side track in Jonesville with many people moving through the cars. You can test the practicability of your devices and other displays by asking yourself these questions concerning the probable reaction of Brown and Smith: Will it attract their attention? Will it arouse their interest? Will they remember it? Will it bring a response from them? These are generally recognized aims of advertising, and they apply equally to exhibits which are, after all, a form of advertising. USE OF THE SPACE FOR DISPLAY For displaying exhibits to moving audiences, the use of the space should be so planned that it is easy to keep visitors moving in a given direction and at the same time make it possible for them to grasp quickly the meaning of what they see. The majority of those who have reported on their experience with trains agree that it is very important that visitors should move in a single direction. This is beyond question desirable unless small audiences are expected; but as is stated elsewhere, capacity audiences are the aim of most enterprises. Having agreed on a one-way movement, there is, however, still considerable disagreement as to the best arrangement of material--whether on two sides of the center aisle, or along the center of the car with an aisle on either side, or finally, with exhibits displayed on one side only with a single aisle. [Illustration: INTERIOR OF HEALTH EXHIBIT CAR An example of the display of exhibits on both sides of a center aisle. If there are many visitors going through the car at one time, they must move slowly along the narrow aisle, looking alternately at an exhibit on one topic on the right, and one on another topic on the left. Both physically and mentally this method of viewing exhibits is likely to be tiring. One would expect the average visitor to carry away a confused impression of the facts and ideas presented.] [Illustration: A WELL ARRANGED EXHIBIT CAR] [Illustration: A WELL ARRANGED EXHIBIT CAR