The greatest deterrent to the growth of air travel is the fear of fire in the minds of potential passengers. It is not a groundless fear, for there must be few members of this Society who have not lost friends and acquaintances from this cause. Unfortunately, the fuel at present in use in all aircraft is of a highly inflammable nature, as is the hydrogen with which airships are filled. So long, however, as oxygen can be kept from mixing with the gas or fuel a fire cannot occur. The problem of abolishing the risk of fire in the air resolves itself into finding the best method of excluding the oxygen from the combustible material. The means adopted must be light, otherwise the aircraft could not use them, cheap and capable of application in any part of the world.