Sketches of the Atomic Clouds As explained previously, it was not possible to make photographs during tha time that the clouds were in the mushroom stage. For about the first ten seconds the clouds were in the firoball stage and were lighted from within by incandescent gases; but after these gases cooled, there was no light for photogruphic purposes wmtil after sunrise. YOKE DAY- the quantity of gaseous constituents in the fireball appeared to be noticeably greater on YOKE Day than TRAY Day, At first, the cloud began to take the characteristic mushroom shape; but for some reason, perhaps its size, the cloud was not able to form campletely the ring shape circulation seen in previous clouds. The primary portion rose as a gigantic bubble of gas without a well defined internal circulation. By the time the cloud reached maxinun altitude, there appeared to be a diminution in volume of the gas bubble because of the large quantity of material left behind in large irregular The blue~violet luminescence did not photograph or provide light so that Photographs of the clouds could be obtained. However, the blue-violet glow did illuminate the clouds so that they wore easy to see mtil they rose high enough to catch the firet of the morning twilight. By the time the luminescence had faded, the upper parts of the clouds were high enough to catch sufficient light to show their details clearly. masses, Throughout, the time that the clouds were visible, they were being rapidly sketched for the purpose of correlating theodolite data, These rough sketches-are the only records of the shapes of the clouds during the time that it was impossible to make photographs, Therefore, since photographs of the mishroom stage are non-existent, it waa decided to make the fullest use possible of the sketches in order to describe the complete histories of the clouds. Most of the sketches were very crude since met of them were completed in less than one minute, and some of the sketches were affected by the preconceived ideas and imaginations of the observers; but by comparing three or more separate sets of sketches reasonably good pictures of the clouds were obtained. This cloud seemad to contain little condensed water vapor, Instead, it seemed to consist almost entirely of dust and smoke, At H-hour plus sixteen minutes, the lowest part of the cloud resembled a swelling cumlus clow reaching to 9,000 or 10,000 feet. This cloud moved away in the easterly winds at low elevations so that there is no record of it after this time. On page 50 is shorm a sketch of the YOKE Day cloud at H: plus one hour. This sketch has been drawn from a colored photogra which shows the same view as the black-and-white photogmph on page 69. Unfortumately, the black-and-white photograph did not print very well, and it is not possible to reproduce colored photographs in this report. Therefore, this sketch is the best available means of showing the shape of the cloud, XRAY DAY-i0 my be noted in the sketch, there was considerable natural cloudiness at H-hour. The tops of the cumlus averaged 8,000 feet and a few reachad 10,000 or 12,000 feet. There were also fractocumilus, and thin stratus around the tops of the cumulus. Passing rain showers had occurred in the vicinity of the test site. The natural clouds, together with darlmess obscured the atomic cloud at altitudes below 10,000 feet, The XRAY Day cloud had the most pronounced internal circulation characteristics of any of the mushroom clouds, In fact, the cloud wery much resembled the ABIE Day cloud at Bikini. The sketches show several short clow) streamers, or spurs, projecting out of the bottom of the cloud as was seen at Bikini; and some of the observers recorded an ice cap, or a smooth veil of cirrus draped over the mushroom at about H-hour plus five minutes. As the cloud rose, the stalk or stem elongated and became smaller in diameter; and at nine minutes and thirty seconds past H-hour, the break which is shown between upper and lower ZEBRA DAY-this cloud had the familiar mushroom form, but the cloud stem of the cloud dispersed and left an irregular patch of smoke and dust. The lowest part of the cloud, which greatly resembled the other did not have a well defined circulation after the second minute. Fro the third to after the eighth minute, there was little change in the general shape of the cloud; but by the ninth minute, the finger-like projection which rose out of the top of the cloud could be plainly seen, This projection rose an additional 5,000 feet above the top of the atomic cloud and reached maximm elevation at about plus 12 minutes. At about the fifteenth minute, the finger-like part of the cloud broke away, but it never did get far from the min body of the cloud. At about the tenth or eleventh minute, the top and bottom of the cloud had shifted so that the top wis east of the broad stom, and observers on the U.S.8. Bairoko were able to look up into the base of what hed been the rising wushroom head, These observers atated that the cloud, viewed from the bottom, had a hollow appearance and looked somewhat like a amoke-ring. There was more cloud material in the edges of the clow! than in ite center. This cloud also had a cumulus-like formation in its lowest and then became lost among the other clouds. and then disappeared as it moved off to the west, cloud masses occurred, This separation occurred at about 20,000 feet. Just below this break, which occtrred in a region of wind shear, the large cumulus nearby, remained visible util H-hour plus twenty minutes portion, —48‘ Thia cumilo~form cloud grew util it reached about 8,000 feet