Surface boats of belligerents will face a-new menace if the incendiary submarine, a four-foot model of which was tested recently, proves successful for war purposes. The menace will be a “sea of fire” which can be made to engulf a vessel by releasing a large quantity of liquid fuel from beneath the surface. In a recent demonstration the model dove underwater and sent up a bubble consisting of six quarts of oil that spread quickly over a 50-foot circle. Chemical detonators released with the fuel turned the mass into a blazing inferno that lasted five minutes, The inventor believes attacks of this kind would be possible against seaports by launching the oil so it would ride in with the tide.