| produced in tha soil, 22 you aosum3s that tho racicnctivity, theo . beta radiation, aftsccticed nranaviily tho top contimetoe £ the teo S011 sursaco as At vould bofove 2t sank du ruch with vonchiny rainfall, it works ont that tho total CS39 in this ono or soil is the Unitod Statas is of the erder ef one red. This is fren all veerons tests. Gf magnitude. contimoter macnituto of This is gust on orces It cerents on the sell vate of loaching, and so on, and one can get move dain grom the published data. The extovnal cama pociation waich is rot confined nearly So close to tho gadionstive Isotescs Locarso it i5 mova ponstrnating has boon at tha lovel cf theoo foevt above tho ground; that is radiation of heman belnss of the order of magnitude cf the total of 6.1 rad, toval Geso to date. PROM TI) FLOOR: What is tho sqvare aroa? DR, DUDLEY: Tho vad is a unit of dese which is inéosondent of aroa--cnerzy dissipation of per gran per matter. n It is throughout the contimoter an averasza of about one ra 4 3 waders ably more on ths mattor of natural vadiation and hanmard lovoels, Lnterpretation of what those numbors mean from him. I would like to emphasize rad, and that is all ia m ooinz to Say about exte2rne: Gamma radiation. I am going to talk bout tha vracicactiva stronL. « foe ~ taumns Waich ara mora khavardors than t ®ne dsoteves, 2 «. “ +. It- is pessible to dstect the radicnctive strontiuna with vory sensitive toannicut and many measuroments have boon mids in tho United States on the