{{explanation}}
3s & 4s start on opposite sides

1-8
: 1s+2s also 3s+4s circle 4H round to left; 1s+2 also 3s+4s set to each
  other on sides & 1s+4s dance in & cast 1 place (2s & 3s dance up/down
  to ends & face out)
9-16
: 1M+4L also 1L+4M in prom hold dance reels of 3 on sides (RSh to 3L/2L)
17-24
: 1M+4L also 1L+4M in prom dance round each other LSh to change places
  & 1s+4s dance LH across.  2 4(1)(3)
25-28
: Dancing couples cross LH to give RH to partner, 1s cross up & cast
  to 2nd place **while** 4s cross down & cast to 3rd place opp side
29-32
: Dancing couples again cross LH to give RH to partner, 4s cross up & cast
  to 2nd place **while** 1s cross down & cast to 3rd place opp side
  ending 2 4(1)(3)