One key aspect of a Square Through (as opposed to n changes of right & left,
cross trails, circular heys, etc.) that hasn't been mentioned, is that after
the last Pull By of a Square Through you do NOT turn. The initial Pull Bys
all have a quarter turn after the Pull By, but the last one leaves you back
to back with the last person you passed, facing in the opposite direction to
them.
Square Throughs or changes of rights & lefts, in ECD, take as many beats as
there is music. Some dances require you to make each change in two beats,
some are more leisurely and allow you four beats for each one. Contra
dancers don't want to use four steps to pull past someone when they can do
it in two steps. Hence the Balanced Square Through: four beats to balance
forward & back; four beats for two changes - making a total of eight beats -
just right for a contra dance figure.
As has been mentioned the "Cross-Trail" found in modern contra dancers is
not really a cross trail; it is much more like two changes of a circular hey
or two changes of rights & lefts, without hands.
Happy dancing,
John Sweeney