  We present the results of our analysis of the geometrical tidal tail
characteristics for nearby and distant interacting galaxies. The sample
includes more than two hundred nearby galaxies and about seven hundred distant
ones. The distant galaxies have been selected in several deep fields of the
Hubble Space Telescope (HDF-N, HDF-S, HUDF, GOODS, GEMS) and they are at mean
redshift z=0.65. We analyze the distributions of lengths and thicknesses for
the tidal structures and show that the tails in distant galaxies are shorter
than those in nearby ones. This effect can be partly attributed to
observational selection effects, but, on the other hand, it may result from the
general evolution of the sizes of spiral galaxies wih z. The location of
interacting galaxies on the galaxy luminosity ($L$) -- tidal tail length ($l$)
plane are shown to be explained by a simple geometrical model, with the upper
envelope of the observed distribution being $l \propto \sqrt{L}$. We have
solved the problem on the relationship between the observed distribution of
tail flattening and the tail length in angular measure by assuming the tidal
tails to be arcs of circumferences visible at arbitrary angles to the line of
sight. We conclude that the angular length of the tidal tails visually
distinguished in nearby and distant galaxies, on average, exceeds 180 degrees.
