0018933 utilized to obtain the samples discussed in Sections 1,3,3 and 1,3.4, Units of the kind illustrated by Figure 2.4 were used for collection of the cloud particle samples needed for the radiochemical work, These samplers were stainleas steel shells of parabolic shape fitted with intake butterfly valves which were open only during the sampling rans. They were installed at the forward end of both the right and left wing fuel tanks of the B-57D's, The particles were collected on a 24 inch filter paper which was supported by a retaining screen located near the aft end of the unit, The coincident sampler was constructed in such a way that both the gas and particle samples would be taken from the same volume of the cloud, Air was drawn through a dessicant section and a filter section by & circulating pump and then forced under pressure into a sample bottle, Figure 2.5 shows the intake and dessicant-filter sections and Figure 2,6 is a photograph of the compressor pumps and gas bottles, These samplers were mounted on both sides of the B-57D fuselage toward the rear of the aircraft, The WB-50's used for the fallout sampling were equipped with the AFOAT-1 standard E-1 filter assembly, Figure 2.7 is a view of a WB-50 with the filter foil installed on top, nearly over the rear scanner's position, Figure 2,8 shows the filter screen removed from the foil witha filter paper in one side, The foil was sealed by sliding doors in front and - Sls