{{explanation}}
2 chords, on 2nd chord 3rd & 4th couples cross to opposite side

1-4
: 1s+2s also 3s+4s set, dance 1/2 RH across.
5-8
: 1s+4s set & dance 1/2 LH across. (2) (4) 1 3
9-12
: 2s+4s also 1s+3s set, dance 1/2 RH across to finish facing clockwise 4 2
  (3) (1)
13-16
: 4s+2s also 3s+1s each chase 1/2 way clockwise into lines of 4 across
  with 2M+4L & 1M+3L BtoB
17-24
: 2s+4s also 1s+3s dance reels of 4 across the set
25-28
: All set & Petronella turn to finish in lines of 4 down/up on the sides
  (2) (4) 1 3
29-32
: All set turning to face partner, all cross RH.  2 4 (1) (3)
33-40
: All dance 8H round & back.  2 4 (1) (3)