The dance starts with two chords.
On the second chord 3rd woman and 4th man change places so that 1st and 2nd couples are facing their partner while 3rd and 4th couples are beside their partner.

This dance commemorates James Hutton (1726-1797) one of Scotland's foremost scientists who is considered the founder of modern geology.
He was one of the first to realise that weathering of rock formations showed the Earth was far older than was assumed at the time.
Most famously he found several "unconformities" where strata of sedimentary rocks clearly overlaid older strata at a very different angle indicating that the older rocks must have been raised up from the sea bed, turned over so the strata were vertical, then sunk again and later covered with new sedimentary layers and raised up a second time.

The cross, cast off and dance down figures indicate build up of the sedimentary layers (perhaps silt carried by rivers and falling to the sea floor).
These are compressed when 1st and 2nd couples end closer together by bar 16 than at bar 9.
The rock layers are turned in bars 17-24.
The last figure has a hint of more sedimentation but is mainly oriented across at the top and up/down at the bottom like a typical unconformity.

For more information about unconformities see <<https://en.wikipedia.org/wiki/Hutton%27s_Unconformity>>. One of the notable unconformities in Scotland is on the island of Arran. See <<http://www.arrangeopark.co.uk/wp-content/uploads/Walk_Leaflets/1.%20Hutton.pdf>> and <<https://www.scottishgeology.com/best-places/isle-of-arran/>>.