In this paper we suggest a simple technique for validating the Goldstein-Wehner law for a stratified positive column of dc glow discharge while studying the properties of gas discharges in an undergraduate laboratory. To accomplish this a simple device with a pre-vacuum mechanical pump, dc source and gas pressure gauge is required. Experiments may be performed in nitrogen or even in air. First you need to photograph the discharge tube with striations at different gas pressure values and then you need to determine the thickness of the first striation on a computer monitor. (Contains 8 figures.)