OnCTSsemeacoe By chemical analysis of the re689 maine the existence of the follow- ing elements are detected: Balt0, 1132, 1133, Tel?F (mn), and ue?! ,, 2195, Nb99, 721, Lath, qi31 | According to Mr. Yokoyama of Tokyo University considerable amount of the trans-uranium element Nj¢°39 (half-life 2.3 days) seems to exist in the rain. On the basis of these observations, it may be concluded that the radioactive rain of middle May results mainly from the Bikini experiment of May 5. The half-life of the radioactivity observed in the rain had become longer and longer afterwards, In mid-September rain of several hundred cpm/l had been observed in Tokyo, the half-life of which being about 60 days. Members of Miyake laboratory of the Meteorological Institute collected the radioactive substances in the air using an airplane in cooperation with the Asahi-shinbun. They found an artificial radioactivity of 0.82.0 x 10o-lecurie/ on the average in the atmosphere 1000 m to 3000 m above sea level, Furthermore, people of Ishii laboratory of the Meteorological Institute tried to detect the artificial radioactivity in the high atmosphere making use of a radio-sonde, They observed radioactive deposits of 70 cpm on a rmmbber balloon (800 g in weight) which went up to 19 km above sea level. activity was found on the upper half of the balloon. Most of the radiois Melee Russian Experiment of Atomic Bomb N . arth 2 pte ede tl ef owe de lS oe, ‘oe It was anticipated on the basis of various information that Russian experiment of atomic borb would be held about the end of August. Thus careful observation of barcmeter has been continued and the half-life of radioactivity hes been measured at each rainfall. Mo definite result has been obtained until September 16 when Tass announced thet the experiment wes over. There wes hardly any morent of relief, however, before the rain which fell in the districts of Tohoku and Hokuriku in the early morning of September 19 was Po nd to carry strcng artificial radicactivity. On Septecber 22, a recordbreaking amount 124,000 cpm/l of radicectivity wes observed in che rain at Yanegata. dust about this time the Typhoon No. 14 left Jepan off Kashina-neéa in the early morning of September 19 and, in turn, the dry end cold eir Sireamed into Jepan from Manchuria erea, The recicactivity was found only in the rain cf Tohoku districts which was supplied by the cold Zfrent line On the other he nd, wnere wes alccst no redioactivity in the rain wrhicn belonged to the warn front iine on the Facific ccest, is thus clear thai the source of this r ratioectvivity is not in Bikini but in some place to the north of Japan. (See Figs. lL and 5). int RH formed by that cold air, ivy ies ery + chim The source of the cold air which ceze upon Tohoku around Sept. c an be treced Lack along the stream line,which presses through ilanchuria én d u th 3 vicinity of the Eerykal lake, to the central or northeestern pert cf Sit rile. it might thus be supposed thet the exrerinent wes done sonewhere in mr he eoestern Siberia or Arctic ccast,