1. The slight dependence of pressure on the cone,angle in Fig. 3 results from the utilization of the tangent-cone predictions13for the inviscid flowfield. The free-molecule limit shown in Figs. 2 and 3 has been computed from the formulae given onpp.401-403of Ref. 13. For large freestream Mach numbers and Moo sin 0c> 1 (valid for the current experiments) the freemolecule limit for heat transfer is adequately given by sin 0c, the value for infinite speed ratio and completely diffuse reflection.Thefree-molecule limit for pressure for completely