The problem of a sphere moving in an infinite homogeneous incompressible liquid has been discussed by many writers. The corresponding problem for a semi‐infinite liquid with a free surface has not been treated earlier.
It is shown that the surface wake of such a submerged sphere is approximately the same as that which would be caused by a traveling pressure disturbance in the atmosphere above the free surface. This is, essentially, a consequence of the Bernoulli theorem.
If the motion is sufficiently slow, the surface reacts to this equivalent pressure as a barometer (equilibrium theory). For more rapid motions, dynamic effects reduce the response of the surface, but leave a wake in the region already traversed by the sphere. The calculation of this wake involves the usual distinction between incoming and outgoing waves, which is introduced in the Fourier transform of the solution. The resulting integrals are evaluated by Kelvin's approximate method of stationary phase.