Life rafts that hold 30 persons are being made of a network of rubber discs strung together with ropes. The discs are formed from a new rubber which has twice the buoyancy of cork and is composed of small cells filled with nitrogen gas. The extreme lightness of the raft makes it especially valuable as a lifesaving aid in torpedo sinkings when there is no time to launch a lifeboat. Attached to the ropes are self-lighting electric lamps which float in the water and guide rescuers to the scene. The rubber, developed by United States Rubber Company, is resistant to oil, acid and fire.