The world’s chief known supply of helium lies in certain sections of Texas, Kansas, Colorado and Utah. More important, United States is the only country having great pipe lines, can distribute natural gas from Texas to cities as far away as Kansas City, St. Louis and Chicago. Without such a market operators would have to separate and release the 95% of natural gas to get the 5% of helium, and costs would be still higher. Helium is perhaps the most useful of the few natural monopolies given to this country. It was only toward the end of the World War, however, that Army engineers worked out a process of separating helium from natural gas. A plant was built at Fort Worth and the first cylinders of helium had reached New Orleans ready for shipment to France to inflate observation balloons when the Armistice was signed. Army, Navy and Bureau of Mine engineers worked thereafter to increase production and cut costs, but as late as 1925 Will Rogers called attention to the fact that the Navy had not been able to get enough helium to supply both the Shenandoah and the Los Angeles at the same time. If one was using the helium the other had to stay home. Two ships, and only one set of helium, he commented. The use of helium cut the casualty list on the Shenandoah, would have saved the Hindenburg. Non-rigid airships have had no fire or explosive accidents since helium came into use as the lifting gas. It was the loss by a hydrogen fire of the Italian-built Roma, after it struck a high tension line at Langley Field in February, 1922, which fixed the policy of “helium only” for U. S. Army and Navy airships. The Army’s C-7 was the first airship to use helium. In building the Pilgrim in 1925, Goodyear followed the same policy—even though it had to pay $125 a thousand cubic feet for helium while it could have obtained hydrogen for $5 per thousand. Further improvements and increasing volume of production brought the cost down in time from $125 to less than $20, and helium expense became relatively unimportant in providing safety for Goodyear’s airship operations. Important too during this period was the Army’s development of tank cars for transporting helium. A large item of helium expense was freight, the cost of hauling 130 pound metal containers which held 170 to 200 cu. ft. of the gas. It took 250 such containers to inflate Goodyear’s smallest ship, the Pilgrim. The tank cars hold 200,000 cu. ft. of gas, almost enough to inflate two Goodyear airships. Experiments with specially woven fabric and the use of synthetic rubber cut down the losses resulting from diffusion, and where formerly it was necessary to remove the helium and purify it every six months, diffusion losses were cut to one or two per cent a month, with purification needed only every other year.