Observation balloons of the U. S. Army are accompanied by trucks which serve both as mobile mooring masts and eleven-ton anchors. A winch mounted at the rear of the truck cab and powered by a 125-horsepower motor raises and lowers the balloon by means of a steel cable more than 4,000 feet long. The balloons are used for “spotting” the fire of the big guns. They have interchangeable motor gondolas and observation baskets, and within ten minutes can switch from a motor-driven airship to a captive balloon. A fleet of trucks carries equipment and spare parts for maintenance and repair of the balloons.