Hi Catbug...and Lesley
I've been doing some scrounging of mah oan!!
I found two more examples of the surname....one on the MC of Henry to Isabella which appears in a slight different hand but just as difficult to discern...still looks like it begins with an R though.....and now just found the MC for Henry's brother George to Ann in 1856.....and his mother's name.....are you ready.........
wait for it........
Ditto
I do believe it is written Ditto..

.the hand is quite good.
Ah'm shaking mah puir heid oan this!!
So I'm no closer to finding the name but there are two MC's out there if you're doing the whole family!
oh while I'm at it....
Here is Henry's wife on the 1881...obviously he was off carting somewhere
Dwelling: 22 St Andrews St
Census Place: South Leith, Edinburgh, Scotland
Source: FHL Film 0224020 GRO Ref Volume 692-2 EnumDist 38 Page 1
Marr Age Sex Birthplace
Isabella AYRE M 33 F Leith No Leith
Rel: Wife (Head)
Occ: Carters Wife
and this may well be Henry's brother George....and perhaps another brother?
Dwelling: 2 Old Bridge End
Census Place: North Leith, Edinburgh, Scotland
Source: FHL Film 0224021 GRO Ref Volume 692-2 EnumDist 60 Page 8
Marr Age Sex Birthplace
Mary ADAIR M 29 F Damillington, Ayr, Scotland
Rel: Head
Occ: Housekeeper
Hans ADAIR 12 M Tarbolton, Ayr, Scotland
Rel: Son
Occ: Scholar
Mary ADAIR 4 F So Leith, Edinburgh, Scotland
Rel: Daur
Jane ADAIR 3 F N Leith, Edinburgh, Scotland
Rel: Daur
James LAING U 28 M Farlane, Aberdeen, Scotland
Rel: Lodger
Occ: General Labourer
Joseph BROWN M 26 M England
Rel: Lodger
Occ: Ship Carpenter
George AYRE W 30 M N Leith, Edinburgh, Scotland
Rel: Lodger
Occ: Carter
Charles AYRE U 23 M So Leith, Edinburgh, Scotland
Rel: Lodger Occ: Carter
John DOMONDOPLE M 37 M Triesta N B S, Austria
Rel: Visitor
Occ: Seaman
Looks like still some more sorting to do!!
Best wishes
Jean