The full Celtic reel is a 16-bar Figure Starting with the Half celtic reel which is then repeated from the new Positions; all Finish where they Started.
The following is a description of the Half celtic reel as it occurs in bars 9-16 of The Celtic Reel, Starting with the 1st Couple back-to-back between the 2nd Couple, Men Facing Ladies, all in line Across the set, half a Place below 1st Position:
Giving right shoulder, 1st Couple Pass the Facing Dancer as though Starting a Reel of four Across the set with 2nd Couple, Finishing 1st Lady Facing Up, 1st Man Facing Down and 2nd Couple Facing each other between them;
1st Couple Chase clockwise on an approximately circular path one quarter of the way around The set to Finish Facing Up and down on the Centre line While 2nd Couple Pass Giving left shoulder to Finish back-to-back on the Centre line between 1st Couple, 1st Lady Facing 2nd Man, 2nd Lady Facing 1st Man;
Both Couples repeat bars 1-2 from new Positions as though Starting a Reel of four on the Centre line, Finishing 2nd Man at the Top Facing the Ladies' Side, 1st Couple Facing each other between 2nd Couple and 2nd Lady at the Bottom Facing the Men's Side;
Both Couples repeat bars 3-4 from new Positions, (2nd Couple Chasing) to Finish as at the beginning of bar 1 but all now having Exchanged positions with Partners.
It may be helpful to remember that, whenever the Dancers are Facing each other ready to Exchange positions at the Ends of the modified Half reels of four, they are always Man Facing Lady and never Partners.
Note that, the Phrasing of the modified Half reel of four part of this Figure requires 6 bars rather than the normal 4: 2 bars are used for the End Dancers to Pass the Facing Dancers, 2 bars for them to Dance ¾ round each other in the Centre and, finally, 2 bars to Pass the Facing Dancers and so reach the other End of the modified Half reel of four, leaving 2 bars for the Chase.
Note also that, the path of the Chase is actually elliptical (with the shorter axis Up and down) in order to avoid a collision between Dancers in adjacent Active sets.