perpendicular, i.e. 0° is on the perpendicular to the interface heading away from the soil half space. We see from the figure that these distributions peak at around 70° - 80° for h = 1 meter, 40° - 60° for h = 100 meters, and 30° - 40° for h = 300 meters. The height of the peak decreases as the source energy decreases while the "skyshine" (photons travel- ing toward the ground) increases (see Table 4). As the detector height increases, the "skyshine" for a given source energy also increases. The flattening out of the angular distribution as the source energy decreases becomes more pronounced as the detector height is increased. The angular distributions of the scattered and unscattered y-rays are quite comparable (see Figure 6) to the total exposure angular distributions although the unscattered distributions are slightly more peaked. The angular exposure rate distributions for 40 K, 238 U, and 7%* 7h (Figure 7) are similar. to those for :364, 1.0, and 2.5 MeV sources shown in Figure 5. There is little difference in the three distributions for h = 1 meter and only slightly more for h = 100 meters. Skyshine contributes 11% of the *°xR exposure rate, 13% of the a3ey exposure rate, and 12% of the 7°* Th exposure rate at h = 1 meter and 12%, 15%, and 13% of the exposure rate at 1 = 100 meters. The natural exposure rate angular distribution, therefore, is fairly insensitive to the relative amounts of *°K, 7°"u, and *7* Th in the soil although it does vary with detector height. Thus, a detector with an angular response must be calibrated properly with elevation in order to interpret readings of natural gamma exposure rates made at various heights above the interface.