Hi,
I think I may have found their marriage in Australia.

Thomas CLAUSON married Elizabeth CORVIE [I believe that this
just might be Cowie]. Married 1881 at Redfern NSW (Reg year 1888) Registration number 20276.

I could be wrong but I think Corvie should be Cowie.

If you try Ancestry Australian Marriages (do a google if you can't find it) The google brings up a list - click top item. ....Fill in Thomas Clauson only and 1881.
It should come up.

Oddly enough, another marriage with the same names also comes up, dated 1916. ... I don't believe that!

Brian, Glasgow.