THE BUTTERFLY.
Longways Duple Minor Set.  (Suitable for ceilidh, probably.)
Barnes, CDB-1.

A. Hands across with first and second couples. 
B. First and second couples pass under four times. 
A2.First and second couples swing and cast one (progressive). 

Partners hold between them, in their right hands, an handkerchief, or two
handkerchiefs tied together.

The "swing" is danced to the following step:-

   L  R  L   R L R  L R L