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Classification of the Sci.
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transportation of freight nor even for ordinary passenger traffic. What peculiar advantages would conveyance through the air possess. One only: namely, the airship being free to move in three dimensions, the likelihood of its track being intersected by that of a second such ship would be next to nothing. It could therefore elude all pursuit and pass every barrier. Its one utility will therefore be for carrying information to otherwise inaccessible points and for bringing information back. It can go to High Tibet, Central Africa, Central Australia, the two poles. For such purposes a speed through the air of twenty miles an hour would be desirable, but half that will do. But what is indispensible is that when it gets out of order, its crew should be able to put it into perfect repair and almost build a new one, no matter in what desert or forest they may be. This prohibits motor machinery. It must be of the utmost simplicity, must carry three men with their stores, and must be easily managed without fatigue by a single man. Is this possible? What expenditure of energy is required to sustain