A layer of very viscous liquid (e.g. tar, molten glass) spans a chasm
between two vertical walls. The slow fall or slump of this initially-r
ectangular liquid bridge is analysed. A semi-analytical solution is ob
tained for the initial motion, for arbitrary thickness/width ratios. T
he formal limits of large and small thickness/width ratios are also in
vestigated. For example, the centre section of a thin bridge of liquid
of density rho and viscosity mu, with width 2w and thickness 2h much
less than 2w falls under gravity g at an initial velocity rho gw(4)/(3
2 mu h(2)). A finite element technique is then employed to determine t
he slumping motion at later times, confirming in passing the semi-anal
ytical prediction of the initial slumping velocity.