Regelation: A supplementary note

In regelative motion of a body through ice smoothness of, in general, either the freezing surface at the rear or the melting surface at the front is unstable. The stability criterion, which is affected by the close proximity of the body to these surfaces, is calculated. A high thermal conductivity in the body promotes the rear instability: its consequence is that the water sheath separates from the body, regelation occurs in an extended wake, and the rate of regelative motion is reduced. The forward instability, occurring with a body of low thermal conductivity, is thought to have less marked observable consequences.