National Geographic : 1951 Oct
553 A Weighted Pipe Line Rolls on Rails into Its Tennessee River Bed. Tractors Inch It Along Some gas lines cross turbulent or erosive rivers by hitching rides on railroad or highway bridges or their own suspension spans (pages 549, 554). Most lines, however, are buried beneath rivers. Concrete blocks girdle this 26-inch artery of the Texas Gas Transmission Corporation. The 800-mile line runs under 15 rivers, in cluding the Mississippi and Ohio.