The spreading of an elastic adhesive sphere on a substrate is calculated us
ing continuum elasticity theory and the van der Waals interaction between t
he solid surfaces. The deformation and contact area are obtained self-consi
stently as a function of lend. Hysteresis is demonstrated between the loadi
ng and the unloading cycles: the receding contact angle exceeds the advanci
ng one. In addition, for a given deformation (flattening), or fur a given a
pplied load, the receding contact area exceeds the advancing one. This none
quilibrium phenomenon is velocity dependent and in accord with experiments
on adhesion and crack propagation.