Major regions of inhomogeneity are present in the mantle at depths less than 1000 km. The thermal gradient also greatly exceeds its adiabatic value at relatively shallow depths. Hence the Williamson‐Adams equation cannot be used in this part of the earth to derive the density variation from seismic data. In this paper the density in the upper mantle is obtained by explicitly introducing the constitution of the material there. In the lower mantle the extended Williamson‐Adams equation is used, and the constitution of this region is deduced from the density curve. Recent seismic results for the upper mantle, particularly those relating to low‐velocity zones, are examined. Significant regional differences are present. Beneath the oceans there is a definite LV zone for S, and possibly one for P as well. Beneath Precambrian shields the LV zone for S is less pronounced, and the LV zone for P seems to be absent. Other continental regions are intermediate between these zones. The LV zone is considered to be due to high thermal gradients with mineralogical and chemical heterogeneity superimposed. Differences between the behavior of P and S are largely due to different temperature coefficients of the two velocities. Regional contrasts arise from regional differences in thermal gradients and mineralogy. Consideration of temperature‐depth relations leads to the conclusion that the mantle is hottest beneath the oceans because of the absence of a thick, radioactive crust, and coolest beneath Precambrian shields because of low heat flow. A self‐consistent model of the mantle requires that the thermal flux at a depth of 400 km be about 0.5 μcal/cm² sec, because geochemical evidence indicates that the K/U ratio in the upper mantle is much smaller than in chondrites. The self‐consistent model requires very high thermal conductivity at high temperatures, such as would be provided by radiative transfer or possibly by movement of material. Petrological models of the upper mantle are constructed on the assumptions of an over‐all pyrolite (ultrabasic) composition and an eclogitic composition. Densities in the mantle are then calculated from known densities, thermal expansions, and compressibilities of minerals inferred to be present. Corrections for the effect of pressure on thermal expansion and compressibility are made from results of the theory of finite strain. The transition zone, at depths between 400 and 1000 km, is the site of a series of major phase transformations leading to close‐packed structures with silicon in sixfold coordination. The density curve in this region is approximated by a linear increase in density with depth. The lower mantle, between 1000 and 2900 km, is considered to be homogeneous, and the density is computed from the Williamson‐Adams equation, modified in some cases to take account of a superadiabatic thermal gradient. The magnitude of the density increase in the transition zone is adjusted to satisfy the restrictions imposed by the total mass and moment of inertia of the earth. A complete density curve ...

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Compressional and shear wave velocities (Vp and Vs) have been measured to 10 kbar in 17 granulite facies rocks and 15 eclogites. The former included quartzo‐feldspathic, gabbroic, and garnet granulites as well as mangerites from the Adirondack region. The eclogites included the three types described by Coleman et al. from California, Norway, South Africa, and Tasmania. The mean ranges of the values of (∂Vp/∂P)T and (∂Vs/∂P)T in the 8‐ to 10‐kbar range are slightly higher (0.015–0.022 and 0.008–0.012 km/s kbar) for eclogites than for granulites. Velocity‐density systematics, based on the 10‐kbar data, is evaluated in the light of Birch's law, D. L. Anderson's seismic equation of state, Wang's C‐ρ relation, and the K‐V relationship of O. L. Anderson and Nafe and D. L. Anderson and O. L. Anderson. On close analysis, there is a distinction in Wang's relations for M¯ ∼ 21 and M¯ ∼ 22. Most of the granulites and eclogites have M¯ values of ∼22; Birch's relationship for these and previously studied basalts ( M¯ ∼ 22) is Vp = −1.85 + 2.87ρ, where r2 = 96%. For Vs the best fit of the data for granulites and eclogites ( M¯ ∼ 22) is Vs = −0.33 + 1.40ρ, where r2 = 88%. The best‐fit equation for Vs that includes the calcium oxide effect in all the granulites and eclogites is Vs = −0.63 + 0.21(21 − M¯ ) + 1.56ρ + 0.016 [CaO]. On the basis of the laboratory results, it is shown that elastic properties of garnet granulite with M¯ ∼ 22 are compatible with those of the 7.1‐ to 7.8‐km/s crustal layer. Analysis of crust‐mantle seismic data in various regions, and the present laboratory results, shows that the assumption of M¯ ∼ 22 for the lower crust as well as for the upper mantle fits better than M¯ ∼ 21. On the other hand, the M¯ ∼ 21 model fits better for some geophysically anomalous regions in the western United States.

The melting curves of the alkali chlorides and the sodium halides have been determined at high pressures. The results can be represented within experimental error by Simon's equation. Comparison of the slope of the melting curve at low pressure with measurements of the changes of volume and entropy upon fusion suggests that the latter data are systematically in error.