81 others. These data were also reported by Eisenbud and Harley. (425) The network since 1954 has been quite stable. ° In January 1959 it consisted of 46 U. S. stations, 68 elsewhere in North America and overseas and 64 maintained in cooperation with other countries through the United - F Nations, As the approach to fallout problems became more sophisticated, it was desirable to have a measure of individual radionuclides, particularly sr90 various geographic areas, tame, and to have an estimate of the gamma dose delivered to the population in Actual gr70 measurements could best be performed on monthly samples but, because of the radiochemistry involved, this collection system grew very slowly. It was apparent that it woyld be very use- ful if a reasonable estimate of the Sr” deposition could be made from the total beta measurements on gummed film, In the period before megaton weapons were fired, the radioactive debris stayed in the troposphere and was cleared out with an average life of about one month. Thus, it was usually possible to attribute fallout to a single f burst and to make reasonable estimates of the gr? content based on total beta measurements. SS oF i i It was also possible by a knowledge of the nuclides pro- duced, to estimate the infinite plane gamma dose. The original calculations of Sr70 deposition from measurements of total beta activity on ashed gummed-film samples-.were performed as follows: 1, The activity measured on a given sampling day was attributed to the test immediately preceding that sampling day. 2. The measured activity on the counting day was extrapolated to a I too oF we , fixed day (usually the first day of the following year) by the formula ie pee pa . kr. po r ' 4 hk ; bs pe bs al bs F 4 bs i ye -