From Figure 11 we see that the ratio of the exposure rates at h = 1 meter even for two sources quite far apart in energy does not depend on the depth distribution. This is important since often one can make the assumption that two isotopes are distributed similarly with depth. If one then has an experimental measure of the ratio of their activities at any depth one can, using the results of this report, estimate the ratios of their exposure rates. If an independent measure of the total exposure rate can then be made, a fairly complete picture of the radiation field can be deduced. A more detailed examination of the variation in exposure rate with detector height is shown in Figure 12 where the ratios of the exposure rates at 10, 100, and 300 meters to that at 1 meter are plotted for different source distributions. Here we see that the 10 meter/l meter and 100 meter/1l meter ratios do not vary too rapidly with source energy. Sindée over a wide range of depth distributions this ratio changes by only a factor of about 2, one can make reasonable estimates of the exposure rate at ground level using Measurements made from an airplane or helicopter even if the exact source spectrum of the radiation is unknown. This fact could be of importance for some types of emergency radiological surveying procedures. Figure 13 indicates the ratio of the exposure rate due to scattered y-rays relative to the total exposure. The shape of the curves for h = 1 meter and h = 100 meters is fairly similar, reflecting corresponding dependence on source energy. The percentage of the scattered component to the total, as determined from Figure 10, however, is much more dependent on the source depth distribution at h = l meter than it is at h = 100 meters. This again indicates the increased effect of the extra soil cover on exposure rates at lower detector heights relative to higher altitudes. The fractions of the total exposure rate due to "skyshine" are given in Table 6. The "skyshine" is quite