Abstract
The β-activity of fission products in surface air are analyzed in a diagram, with latitude and time as coordinates. Spring-season maxima and spread of new debris are readily discerned. Debris from 1961 Soviet testing, traveling by way of the upper troposphere or the stratosphere, arrived at 16° to 35°S more than a month before debris transported through the troposphere. A maximum lateral-diffusion coefficient of about 4 x 105 m2 sec-1 is implied for the tropical troposphere, and a much larger value in middle and high latitudes. Debris in the troposphere from United States testing at 2°N spread mostly into the southern hemisphere.