The power for the lantern would be obtained in the ordinary manner from tanks of oxygen and hydrogen carried in the car. A car containing the lantern equipment would be entirely self-contained and no electric wires or other attachments would be necessary. The lantern car would be stopped the proper distance away from the lantern screen on the other car, and the slides could be shown on the screen within three minutes after arrival in any desired section of the city. In thickly populated districts it would probably not be necessary to announce a political meeting of this kind, as word would be passed very rapidly that a lantern talk was in progress and the desired crowd would collect spontaneously.

340 GRAPHIC METHODS

One very great advantage of the lantern presentation in political work comes from the fact that after one good set of slides has been prepared, these slides may be duplicated at very small expense. Twenty or even fifty sets of slides might be shown in different parts of a city simultaneously on the last few nights just before election. The main candidates are never able to make speeches at all of the desired points during the last few days, and they probably always feel that the last days or hours before an election are the most valuable of the whole campaign. When many sets of lantern slides are made from the same original charts there is very little additional expense, and the number of people who may get the benefit of the carefully prepared slides is tremendously increased. In every city there are many young lawyers or business men who would be willing to make a speech to accompany the slides if they could depend upon the slides for their main material. The number of people who may be reached during the last few hours of a campaign is thus almost unlimited if the lantern-slide method of presentation is used.