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

1-8
: All set, 1s & 4s turn RH 1/2 way **while** 2s+3s cross RH, 1s & 4s lead
  into centre & dance RH across 1/2 way **while** 2s+3s cross back RH
9-16
: 4s & 1s lead out of ends, cross & cast back to centre to face 1st crnr
  pstns (M face M in diag line), all turn LH to end 4 2 3 1 (3s+1s on
  opp sides)
17-24
: 1s dance reel of 3 with 3M (3M+1M give LSh & 1L dances up to give RSh to
  partner) as 4s dance similarly with 2M all loop round to end 4 2 1 3
25-32
: 1s dance similar reel of 3 with 3L as 4s dance with 2L all loop round to
  end 2 4 1 3
33-40
: All Adv+Ret & turn RH