If war should cut off overseas sources of tin, silver might be used as a substitute. Silver-lined food cans, for example, could replace tin cans. A sheet-steel base plated with copper and then with silver only one-millionth of an inch thick has produced a superior food container. Silver would also fit into national defense plans as a met al for high-grade motor bearings, or, alloyed with aluminum and magnesium, for aircraft construction. The photographic industry may use less silver in the future, due partly to the growing popularity of color films and partly to the recovery of hitherto wasted silver in the development of films and prints. One promising field for large-scale use of silver, however, is in disinfecting city water. One part of silver in ten to twenty million parts of water will render even heavily infected water safe for human consumption. The cost would be small.