  In this paper we re-examine the flow produced by the normal impact of a
laminar liquid jet onto an infinite plane when the flow is dominated by surface
tension. It is observed experimentally that after impact the liquid spreads
radially over the plane away from the point of impact in a thin film. It is
also observed that, at a finite radius, there is an abrupt increase in
thickness of the film which has been identified as a hydraulic jump,and that
this radius is independent of the orientation of the surface showing that
gravity is unimportant (Bhagat et al. 2018). We show that the application of
conservation of momentum in the film, subject only to viscosity and surface
tension and ignoring gravity completely, predicts a singularity in the
curvature of the liquid film and consequently a jump in the depth of the film
at a finite radius. This location is almost identical to the radius of the jump
predicted by conservation of energy and agrees with experimental observations
