damage the skin results in early deatha from damage to the bons marrow and the deep organs, Thus the skin burns observed in the Japaneses casualties from the Hiroshima and Nagasaki bombs were not the result of ionising radiation and were caused chiefly by thermal radiation. Fallout radiation associated with these bursts was insignificant. 2 CHARACTERISTICS OF FALLOUT MATERIAL. The chemical and physical make-up of fallout will vary according to the type of terrain or soil over which the detonation occurs. 411 fallout is par- ticulate in nature, but the size of the particles will depend to some extent on the physical and chemical characteristics of the soil. The fallout assooia- ted with the Castle detonation, March 1, 1954, waa a white, powiery matorial largely composed of incinerated coral. Aside from the radioactive component, the calcium oxide of the material was in itself irritating to the skin due to its caustic nature. Moreover, it was probably pertly dissolved in the perspira- tion on the skin, thus increasing its irritating eaétion. This alac may have enbanced the radiation to the akin by bringing the radioactive materials in closer contact with the skin, The presence of irritating chemicals on the skin ia known to enhance the radiation effect (MacKee, Cipolarro and Montgomery). Fallout produced from other types of soil, not predominantly coral, might vary considerably in chemical and physical make-up and ability to irritate the skin. Color and particle size would also vary, Yor instance, siliceous type soila would probably form mich less irritating fallout. The particulate nature of the material results in a spotty distribution of lesicns on the body. The Marshallese claimed that the material adhered closely to the skin and was difficult to brush off. This was borne out by the difficulties encountered in decontaminating the skin of the exposed individual S.«