Huddling behind a barricade of sandbags, spectators recently witnessed tests of a liquid oxygen-and-carbon bomb developed by Lester P. Barlow and his colleague, B. G. Holderer. To show that fire and shock will not explode them, bombs were burned, rifle bullets were fired into them, they were shot out of a trench mortar 500 feet into the air, and shot against a steel plate so they ricocheted 300 feet. But when an eight-ounce charge was detonated by a blasting cap under logs, it reduced them to matchwood and hurled fragments high in the air. According to Mr. Barlow, the explosive, which is made by soaking carbon and other secret substances in liquid oxygen, does not deteriorate until about thirty hours after saturation. While liquid oxygen explosives have been used for many years, the inventor claims his bomb has a great killing potency, which is said to result from unusually powerful pressure waves. Another advantage claimed is low cost of manufacture, said to be four and one-half cents a pound.