  A fluid in the NVT ensemble at T less than the critical temperature T_c and
rho = N/V somewhat in excess of rho_coex (density of the saturated gas in the
gas-liquid transition) is considered. For V->infinity, a macroscopic liquid
droplet coexists with surrounding saturated gas according to the lever rule.
For finite V, droplets can only exist if they exceed a minimum size. A
(rounded) first order transition of the system occurs when the droplet
evaporates into the supersaturated gas.Simulation evidence for this transition
is given for a Lennard-Jones model and interpreted by a phenomenological
theory. At the transition, the chemical potential difference mu_t-mu_coex
scales like L^(-d/(d+1)) for a cubic volume V=L^d in d dimensions, as
L->infinity.
