The term pipeline refers to a long line of connected segments of pipe, with pumps, valves, control devices, and other equipment/facilities needed for operating the system. The development of electric arc welding to join pipes in the late 1920s made it possible to construct leakproof, high-pressure, large-diameter pipelines. The US has far more oil and natural gas pipelines than any other nation in the world: approximately 1.3 million mi of gas pipeline and 0.25 million mi of oil pipeline. Pipelines are the least understood and least appreciated mode of transport. Pneumatic pipelines are used by various industries to transport hundreds of solids such as grain, cement, plastics, and even fish for short distances – usually less than 1 mi or 1 km. The former Soviet Union (FSU) is second only to the US in the total length of oil and gas pipelines constructed. Capsule pipelines use either water or air to move freight-laden capsules through pipelines.