In 1978, Hammack & Segur conducted a series of experiments showing the evolution of finite-amplitude waves of depression. The experiments were conducted in a long, narrow tank with a rectangular, vertically moving wave maker at one end. Time series were collected by gages located at five different positions down the tank. These time series suggest that dispersion and dissipation play important roles in the evolution of waves of depression. In this talk, we examine the roles of dispersion and dissipation by comparing the experimental data with results from numerical simulations of the classical shallow-water, Korteweg-deVries, Serre, and Whitham equations along with some of their dissipative generalizations.