On the basis of his experimental studies Hudleston (1973) concluded that Wd/t and maximum layer shortening values were consistent for a given viscosity contrast despite the duration of the experiment and the length of time permitted to elapse before beginning of each experiment. He found that the grid lines deflected sharply in trend at the layer edges. He attributed this to change in viscosity contrast during the experiment and diffusion across the layer matrix interface. The greater the diffusion, less sharp are the deflections of trend lines.