A cardinal's hat is differenced by colour and the number of its tassels,
not by its shape, which is the same for all clergymen. Thus, for simple
priests, a black hat, with one tassel on either side; for a bishop, a green
hat with three tassels; for a cardinal, a crimson hat with five or seven
tassels. What the reason may be for the variation in the number of the
tassels amongst cardinals, I should be glad to learn.