“In some localities on Mars, we still use compressed air. The powerful windmills are always compressing air for the compressed-air engines. Our compressed-air engines are almost similar to yours, but with you the compressed-air engine is not a success on account of your limited storage room for the compressed air, and also on account of occasional local calms, during which time your supply of compressed air becomes exhausted. “We have overcome these difficulties. The communities of a large area of country are all connected by large air-tubes, into which the windmills are compressing air. At certain intervals along these air-tubes are capacious air chambers for the reception of air. These air-tubes are all around the communities the same as the motor-lines, passing through all the ‘big-houses,’ warehouses, factories and mills, where they drive compressed-air engines, which furnish all the motive power for generating electricity and do all the other motor work. Thus you see by this arrangement, we have a vast supply of air on hand, and there is always a local wind somewhere over this extensive district of communities which are connected by these air tubes. “Where electricity is generated and stored directly by wind power, which it is most places, the electric currents are led through all the buildings, ‘big-houses,’ warehouse, factories, mills and barns. Here it is used for heating, lighting, and motive power for loading and unloading and for running machinery. Waterpower is also largely used for the generation of electricity. Our carriages, farming machinery, and all other movable vehicles and machinery, are propelled by the electric storage battery cell. These cells are with us now very simple, powerful and lasting. Every community has a large supply of them stored for reserve, the same as you have a supply of coal on hand, and our model windmills and waterfalls are charging them faster than we need them. The force which manifests itself in the current of air which drives the windmills is stored for future use, and this storing is being done just the same, whether it is winter or summer, whether we work or sleep. The _irregular_ motion of the wind is thus changed into a perfectly _uniform_ motion of electricity and then applied to machinery.