0018933 mately equal to the diameter of the cloud, The wind structure described in the preceding section on the formation of the light and variable layer 2lso leads to isolation of the 55,000 foot height line along the eastern periphery of the fallout curtain, This situa= tion is advantageous for height line sampling since the aircraft may proceed westward from a position east of the fallout arez and collect the first fallout encountered, i The samples should contain 55, 000-foot fallout 2lone,uncon= taminated by material from the rest of the cloud. Other types of wind structure will probably not be as favorable for height line sampling and the fallout collected is likely to contain particles originating from different levels in the cloud. As one proceeds outward frem ground zero along 2 height line, the particle size of the fallout decrezses and the time of zrrival increases, However, low altitude sampling ata given location should provide a sample containing particles of relatively uniform size.¥ Hence, by m2king 2 series of collections along 2 height line at different distances from the shot peint, edvantege can be taken of perticle size separation by nzturel fzllout processeS. The WB-50 operations were arranged to utilize this situation to obtain a set of samples suitable for an investigation of size-dependent * Uzed synonemously with falling rate. 38 Batt ieOS TFT eftO