3.3. Secondary Parameters: the "Inclination Class"

To describe the appearance of a galaxy with satisfactory completeness at this preliminary stage, a purely geometrical parameter has been added to specify the approximate degree of tilt in the case of flattened systems. This "inclination class" resembles that of Hubble for elliptical systems, and describes the degree of superficial ellipticity of the inclined system by integers from 1-7; systems having spherical cross sections are of inclination class 1; zero is not used, because of the danger of ambiguity with class S0 of the Hubble system.