wing tank filters showed an improvement in sampling performance over the old type. In several shots these new filter tanks allowed samples to be obtained when conditions were such that no samples would have been obtained with the old units. Prior tol October details of the Ivy sampling operation will be worked out and practiced in dry runs with the airplanes. The use of a B-36 as an observer airplane for sampling control has been discussed with TG 132.4 and agreement reached as to the general principles involved in its use. It was found as a result of Tumbler-Snapper experiments that certain methods and techniques planned for Ivy would need major revision. Program 2 experiments may be cited as examples. Projects 2.2, 2.3, and 2.4 have been greatly changed from the techniques crigtnat:y -jenned, ~ 18 - [7