es 0018933 paper was removed by burning off in a stream of atomic oxygen from a gas discharge generator, The maximum temperature reached during burnoff was around 200° C, The weight of material recovered varied from 50 mg, to about 4.5 gm. At UCRL some of the cloud samples were separated into coarse and fine fractions using a Bahco centrifuge and fall rate distribution curves were determined for the two fractions with the micromerograph. Fall rate data were also obtained for all the height line samples and in several cases the specific activity-fall rate curves were determined for cloud and fallout samples. In operating the micromerograph the weight could either be re- corded continuously or in 16 increments by means of individual pans on a rotating turntable. Two of the height line samples and three cloud samples, separated into coarse and fine fractions with the Bahco, were transmitted from UCRL to NRDL for examination, The chemical substances present in these samples were identified with the polarizing microscope and by X-ray diffraction, and the particle size distributions determined by microscopic observation, A binocular microscope fitted with ocular micrometers containing a linear scale was used for the particle work. Each scale division of the micrometer represented 15 microns for the magnification used (100X). A SAN BRUNO ER portion of the sample was placed on a microscope slide and tapped gently 63 G>