Shear and longitudinal velocities were measured by the ultrasonic phase comparison method as a function of pressure to 8 kbar on synthetic glasses of basalt, andesite, rhyolite, and quartz composition and on natural obsidian. Velocities of most of the glasses decrease anomalously with pressure, but increasingly more‐normal behavior occurs with decrease in SiO2 content. The pressure derivatives of rigidity and bulk modulus increase linearly, from −3.39 to −0.26 and from −5.91 to +2.09, respectively, with decrease in SiO2 content from 100 to 49%. The change from negative to positive in the pressure derivatives of both moduli and observed at Poisson's ratio of about 0.25 is consistent with the Smyth model for the anomalous elastic behavior of glass. If the temperature in the upper mantle is about 1500°C, tholeiitic basalt would be molten in accordance with the partial melt explanation for the low‐velocity zone; at 1300°C and below, basalt would be in the glassy state, especially if more felsic than tholeiite. At a temperature of 1370°C and at 30 kbar, reasonable values for the upper mantle at 100 km depth, the basalt glass of this study would have a viscosity of about 1013 P. On the basis of the theory of viscoelasticity the glass would support shear wave propagation at frequencies above 0.1 Hz. Under such conditions of PT, 10 to 30% basalt glass in a matrix either of eclogite or olivine would reduce the seismic velocities by 3 to 9% and could also account for the values observed in the low‐velocity zone.

Temperatures were measured in three closely spaced holes that were cored into quartz‐mica schists near Washington, D.C. Measurements at several times during the 10 months after completion of drilling showed that the drilling disturbance had a negligible effect on the temperature gradients. The isothermal surfaces were observed to be essentially level. The mean gradient in the three holes is 15.7°C/km at depths between 300 and 1000 meters below sea level. The mean principal conductivities of the anisotropic schists cored from the holes are 6.62±0.75 and 8.61±0.17 meal/cm sec °C in directions perpendicular and parallel to the plane of foliation, respectively. The mean conductivity in the vertical direction is 7.13±0.58. The heat flow is 1.1±0.1 μcal/cm2 sec without correction for climatic change. The heat flow is close to other values (1.02, 0.97, and 1.05) reported for other localities in the metamorphosed rocks of the Appalachian system, but it seems significantly higher than some of the values in the Appalachian foreland and Valley and Ridge province.

Temperatures were measured to a depth of 312 m in a hole cored in granite at 36ø52.15'N, 77ø54.15'W (elevation 116 m), near Alberta, Virginia. The temperature gradient in the lower half of the hole is uniformly 18øC/km. The cause of a variable gradient in the upper half of the hole is thought to be movement of groundwater within the hole. The average thermal conductivity determined from measurements on 0.64-cm-thick disks is 7.8 mcal/cm sec øC, but the average conductivity computed by summing the thermal resistivities of the constituent minerals is 6.2. The corresponding values of heat flow are 1.4 and 1.1 vcal/cm" sec, respectively. The average heat flow in eastern North America is 1.0, and the previously published high in this region is 1.3 tzcal/cm 2 sec. Introduction. Determinations of terrestrial heat flow on the continents number about 100 [Lee, 1963]. 0nly five measurements have been published for the metamorphic zone of the Appalachian Mountains of eastern North America [references in Dimen• and Werre, 1964]. In view of this paucity of data, any borehole that is free from strong thermal perturbations, and from which rock samples have been retrieved, represents an opportunity to supplement knowledge of an important but poorly known geophysical parameter. Site and drilling details. During 1909 and 1910 a hole was cored to a depth of 480 m in granite at 36ø52.15•N, 77ø54.15'W (elevation 116 m above mean sea level), about 1.8 km west of Alberta, Virginia, on the right-of-way of the Norfolk and Western Railway Company, 60 m east of mile post 99 and 5 m north of the track.