al In planning for the Eniwetok teats considerable interest waa directed tuwmrds The theodolites were ained at the edges rhich seemad furthest to the left and to the right. There vas no way to direct then to aight on the cloud at any particular elevation and watch the dispersion at just that level. Consequently the altitudes for the manner in which the atomic clouds would be dispersed in the atmosphere, The spread~ inr out of the clouds is important because of radiological safaty and long range detection considerations. Also, the behavior of atomic clouds offers a means of checking which azimuth angles wero taken shifted in accordance with the winds. theories of diffusion and eddy conductivity in the free atmosphere, Data on dispersion were obtained by instructing cheervers to sight on each side of the mushrooms or the prinary cloud masses. It was thought that a rate of dispersion could be derived from the increase in size of these major cloud volumes. The azimuth angles for the sides of the primary masses for each minute hava been plotted on the graphs shown on pages I-31, I-24, and I-27 of Appendix I. The points were con- XRAY DAY- Although most of the cloud mterial was concentrated at 40 to 50 thousand feet, the primary masa extended from about 25 to 55 thousend feet, The right edge of the cloud was urobably close to 45,000 feet, but it is not possible to decide which level was sighted on as the extreme left edge, nor is it possible to tell when the observers shifted from level to level as they endeavored to keep that edge in nected by a smooth curve which represents the results from a single observing station in the position of the Albemarle. Considerable smoothing hea been done in draning these curves ad the irregularities would not be significant in tha computation of a rate of dispersion, After the most srobable azimuth angles for each five minute in- their sights. For a better underctanding of the actual behavior of the cloud see the diagram titled » Page 38, and the terval were arrived at, the diagrams shown on pages 35, 36, and 37 were begun, First, the relative positions of the Albemarle and the primary masses at the times that they reached highest altitude were detarmined, Then lines were dram for the azimuth angles at the five minute intervals, and the bisector of each of the angles formed by the sets of lines was found. These bisectors were dram from the position of tha Albemrle through the centers of the areas representing the primary masses, but they have been erased and do not appear on the final diagram. Next, the direction and velocity of movenant of these primary masses were determined by trial and error methods. Straight linea vere dram through the positions of the cloud masses at the tine that they reached maximim altitude and across the lines directed according to the azimuth angles. In seach case a line could be dram which was cut by the radiating azimith angle linea at more or less regular intervals, Thase lines are paralld§ to the directions of the wind which acted on the cloud mases, and the lengtha of the segments of the lines are proportional to the wind velocities which moved tha cloud material, The directions and velocities obtained in thio manner vere then commared with the estimated rinds and the most probable directions of movenent decided upon. In this manner the locations of the centers of the cloud masses were fixed at five minute intervals. Then, with the centers located, circles could be drawn with circumferences on the two corresponding azimuth enple lines, In this way, the series of expanding circular areas was obtained. Jt was realized that the cloud areas were not actually circular, but a circle was thought to be the most feasible eréa which could be used. These circular areas have been outlined in a manner rasembling the edges of clouds, and straight lines connecting their perimeters have been drawn. The intersection of such boundary lines gives an angle which appears to be useful in comparing the dispersion of the clouda, If the angle were significant, it would go a log way toward answering many problems of dispersion in the free atmosphere, Further studies show that these dispersion diagrams have little practical significance. The fact that the azimuth angle data could be used in comnutations and that angles of dispersion could be obtained made the construction of these diagrams seen worthwhile, It was not until thought was given to the size and stmpe of the cloud at the end of threo hours that it was discovered that these dingrama had little meaning. The level where the vind velocities were slowest is represented in the angles for the left side of the clouds and the level of hishest winds is represented in the data for the right hand side. No trua measure of dispersion was obtainable while the clouds were visible from Enivetok. However, these diagrams were found to be useful in estimating the dimensions of tha clouds ag shown in the photogrephs, ' photographs, pages 55 througr : YOKE 63, i DAY ~ at the tine this cloud reached highest altitude there wma no well defined primary mass at which theodolites could be sighted in order to obtain asimith angle data. The irregular shape of the cloud is shorm in the photographs on page 65. Then, of the cloud moved away it became shaped as shown in the photo~cruphs on pares 66, 67, and 68, and in the diagrams on pages 40 and 41. & theodo- lite aimed at the top of the cloud at 30 minutes past H-hour would be sighted on a level at about 50,000 feet for « left hand azimuth angle and at a level of about 35,000 fect for a right hand azimuth angle. The difference between the left and right hand azdmuth angles is orimarily a result of the differance in wind directions and Velocities between these tuo elevations rather than the result of diffusion Processes, Of the three clouds, tha YOKE day cloud was least adanted to theodolite observations for dispersion studies, It is interesting to note that the azimith angles for the too part of the cloud indicate that it was acted on by an effective wind of 60 mots rather than a 43 knot wind such as was estimated to exist at 50,000 feet at H-hour. This effect of a 60 knot wind is more nearly in agreement with the 65 Imot wind measured at 40,000 feet at aporoximately two hours before H-hour than with the estinated 43 knots. Also, the higher wind velocity indicates that the position of the top of the cloud probably was beyond point "B* and actually close to point "C" in the diagram titled DeterA C on page 32. This seems to be additional evidence that the cloud reached the tropopause. Hovever, in studying the shape of the cloud at the end of three hours it is thought that the estimated winds are the most representative. ZEBRA DAY <The last of the three clouds did have a primary mass which was The theodolites were oimed at either side of the primary masses, which were ten to more or less wel] defined, and it had left and right hand edges which vere maintained directions and velocities In such a deep layer of air. asimith angles was largely denendent upon the fact that the wind velocity at 28,000 feet was greater than at 20,000 feet. See the diagram en page 42. twenty thousand feet thick, In each case there vere significant variations in wind Because of the rinds alone there was considerable increase in tha width of the clouds as seen by the observers, so that successive observations could be mde. However, the difference betneen the