By use of appropriate approximations the incompressible stagnation-point ablation rate for ice is determined theoretically. The theory includes both melting and vaporization or condensation. To verify the theory hemispheres of ice were melted in a subsonic wind tunnel with controlled humidity. It is found that the effects of heat transfer and condensation are of equal importance in determining the melt rate. The agreement between theory and experiment is adequate.

This paper considers the slow motion of a sphere, permanently and uniformly magnetized in one direction, in a viscous electrically conducting medium. The line of the magnetic poles is assumed to be parallel to the direction of the motion of the sphere. The velocity and pressure fields are calculated by two iterations. The distortion of the magnetic field is also calculated. An expression is obtained for total drag due to the viscous, pressure and magnetic forces.

The hydromagnetic stability of a basic two-dimensional parallel flow of an incompressible conducting fluid in a uniform magnetic field parallel to the flow is considered. By use of the generalization of the Orr–Sommerfeld equation for an electrically conducting fluid, it is shown that any given small wave disturbance can be stabilized by a sufficiently strong magnetic field if the Reynolds number is finite and the magnetic Reynolds number small.

Stability of velocity profiles with a point of inflexion at small magnetic Reynolds number and infinite Reynolds number is considered in detail. Perturbation methods are developed to find stability characteristics in two cases, when the magnetic field is weak, and when the disturbance is a long wave. These methods are applied to the jet and the half-jet, which are both found to be unstable to long-wave disturbances, however strong the magnetic field. Nonetheless, these two flows can be stabilized for any given harmonic disturbance of finite wavelength. The analysis of the jet reveals the surprising result that the magnetic field makes inviscid long-wave disturbances more unstable.

In a recent paper, Stratford has described a turbulent boundary layer with continuously zero wall stress and has developed a theory to describe the flow based on two assumptions. The first is that the flow in the outer part of the layer is affected only by the original Reynolds stresses during the initial development, and the second is that flow in the equilibrium layer close to the wall is determined by the pressure gradient and is independent of upstream conditions. In this paper the same assumptions are used, but more careful consideration of their limitations has led to the elimination of some inconsistencies in the original work and to a theory that gives a better description of some of the experimental results. The principal results are: (i) a criterion for zero wall stress in an adverse pressure gradient of sufficient strength, (ii) the form of the pressure distribution for a self-preserving flow with zero stress, (iii) the mean velocity distribution in this flow, (iv) an estimate of the constant in the 'square-root’ velocity distribution for flow near a wall with zero stress.