4 activity if the original contribution of tal ° to this parent-daughter complex is more than 11.5 percent of the total activity of the combination. The evidence in ‘the records of samples whose analysis was begun early enough for the build-up to show up,points toward their being very little or no tal t produced as an instantaneous fission product. This conclusion is borne out by studies of fis- sicn product yields from yes made by Yaffe, et a1? and Petruska et ai.)3, who report yielas of 6.32 + 0.24 percent of Bat 1 and 6.33 + 0.32 percent of ce? respectively. Since the difference is zero within experimental error, pal t© is not produced as an original fission product./ The samples collectea at ground and ship stations may be different due to fallout fractionation and possible anisotropies in fission-product ejection from the weapons. That there is evidence that one or both of these mechanisms are operating can be ascertained by comparison of the spectra of samples collected at different places for the same shot. No pattern is discernible however, with so few sample collection locations. Therefore it is not possible to say anything more than that there seem to be discrepancies be“tween samples from the same shot which are too large to explain in terms of measurement error alone, e.g., the 330 28 : i ,