What happened to James and Thomas?

I know that Robert, Christina and the children - except for James and Thomas - went to Australia on the Ben Cruachan in 1883. James would have been about 26 and Thomas about 23. They weren't on the passenger list and I haven't been able to find them in the Scotland census for 1881. So what happened to them is a bit of a mystery.

There are a couple of James whose ages fit in the census - one is an Advocate's clerk (a law clerk) but he is listed as born in Orkney (my James was born in Dundee and while we can apply a little license, I think Orkney is just a little too far out of the way).

The other is a Plumber. A sensible trade but unlikely since my James trained as a clerk. Just on the off-chance I checked this James' marriage record - he's married to Susan - and the parents don't match.

Thomas doesn't appear in the marriage records at all.

One thought was that they both died. In the 19th century Scottish city this is a possibility and it would make my search a little easier. But while the mortality rate was high, it would have been unusual two young men who had reached adulthood to just die - particularly young men from a middle class family - the mortality rate tended to be higher among children and the poor. Besides, I've searched the Death register on www.Scotlandspeople.gov.uk and they don't show up at all.

Which just leaves emigration. They're not in the UK Census, so I guess that they didn't just head south. I haven't looked at LDS for the United States and Canada - the prospect of trawling through all those names seems rather daunting.

I spent this afternoon looking at http://mariners.records.nsw.gov.au in particular, Mariners and Ships in Australian Waters. There are a lot of Sutherlands but one that looked like a possibility was James Sutherland 35, of Scotland, who was a crewmember (storekeeper) on the Talune which sailed from Hobart to Sydney.

hmmm. I shall have to go away and think about what I can do with this information. Any suggestions would be gratefully accepted.