EDTA RECS GEC REST arnt Ferna gerae —_ 1.2.1 — 0018933 ( ~ Formation and Nature of Fallout Particles, Whena surface burst is detonated, great quantities of the edjacent environment are swept upid mixed with the incandescent air in the fireball, There is sufficient thermal erergy in the hot gas to completely vaporize all the material in the immediate vicinity, but the flow cf heat into 2 massive object, such as a shot tower, sbield or coral rock, will be comparatively slow even with a high temperature gradient, Consequertly, the intericr portions of large structures in the neighkorhood may not receive ercugh heat to evzporate and will be melted only, Later, wher the fireball has risen above the surface, the material czrried ixto it by the vertical zir currents zround ground zsro will not be hezted to the melting point. As 2 result, the fire- bell in its later stzges will contzin the exvizonmental comporenrts 28 a mixture of solid particles, molten dreps azd vapor, The extrancous ma- tide terizlin the Pacific sbets will cons st of ceral and ocean water s2lts ples the cemponments cf the device, shield, and tower or barge. The preponderance of cxygen and cf the eayironmsntzl meterial in fl the firebzll is cf outstzading impartizce in the forme fon cf the fellout péerticles, As the hot zir coolg threugh the range 2500-1000 K°,, it be- comes s2turated with respect to the vaporized cozstitvents end they cen(Reference 3) dense ott as an aggregate cf ligzid Crops most of which are very small (References 4 and 5}, Theee are rnixed with the lerger drops formed by