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C. Lomnitz has shown that creep of rocks under sustained stress increases logarithmically with time. Data for the variation of latitude and seismic waves indicate that for most of the Earth's shell a term in tα, with α about 0·17,is better. This rule is applied in the present paper to the subsidence of a harmonic surface inequality. The indications are that this type of creep will not account for isostatic adjustment within a geological period, and the presumption is that the adjustment is due to fracture or flow near the elastic limit.