SPONTANEOUS COMBUSTION (Lat. span taneus, willing, of one's own accord, from sponte, abl. sg. of *spans, will). The ignition of sub stances at a given moment apparently without the intervention of any causative agency. The spontaneous combustion of organic materials is a frequent cause of fires. When large quantities of soot, linen, paper, cotton or woolen stuffs, ship's cables, etc., are soaked with relatively small amounts of oils (especially drying oils) and ex posed to a limited access of air, they may be ex pected to take fire sooner or later. Similarly, trimmings of lamp-wicks have been known to take fire if kept in open hoxes. The presence of moisture frequently aids spontaneous combustion, and piles of damp hay, freshly mown grass, some times take fire spontaneously. The phenomenon is not, however, without a clearly defined cause. Fats and oils can be shown to undergo a slow pro cess of combustion at but slightly elevated, if not at the ordinary, temperatures. This fact may be demonstrated by placing a little oil on a hot (but not red-hot) metallic surface, when the combustion of the oil will cause a peculiar odor and will render the oil faintly luminous in the dark. The combustion of a small amount of oil
causes the evolution of a corresponding amount of heat; the consequent rise of temperature ac celerates the comlmstion, and hence produces a further elevation of temperature, and so forth, until at a given moment the temperature may become so high as to cause the inflammation of the oil, and with it of the entire mass of organic material containing it. The more porous the ma terial, the greater the surface of oil exposed to the air, provided the amount of oil is not large enough to fill the pores completely. Free ac cess of air might prevent spontaneous combus tion by effecting a lowering of the temperature; nor could combustion take place if too little o• no air at all were admitted. As to the spontaneous combustion of human bodies, it is an impossibil ity, and all reports of such cases can be clearly shown either to be due to erroneous observation o• to he intentionally fraudulent. See PYRO PHORITS.