places certain requirements on the medium. At a minimm for the purposes of crater investigation, it is required that the properties of the medium at equivalent locations (scaled) in two experiments must be identical. This requirement is completely met if the two media are homogeneous, isotropic, and identical. The properties of earth, however, are greatly affected by overburden pressure. Thus in a static sensethe properties of earth are grossly dependent on actual (not sca- i): depth below the surface, and in a dynamic sense these properties wild| similarly affected by the pressure produced by the explosion. Thus’ one of: the fundamental conditions for the proper application of simple scaling laws is violated. The greater the range of size of ex~ plosion, and hence of depths, the more serious this violation becomes. A further.aifficulty with the application of theory occurs in situ- ations such as:existed on CASTLE, where two media, earth and water, were involved, and where the earth was saturated so that forces were transmitted by a complicated combination of intergranular forces and hydraulic pressures. 17