Thanks for your messages, Alan. The website doesn't seem to let me send personal messages yet.
Catherine (the little girl) was born around 1858 so unless she was much older than she looked in the picture it can't have been taken as late as 1874.
I exchanged e-mails a few years ago with a descendant of James T in New Zealand, so if your cousin's wife is interested I could try to put them in touch.
Regarding Milnes, the north east of Scotland is infested with them. The Milne connection that I mentioned is from Alexander & Mary's daughter Susan, who married a Mr Milne.
Best wishes from Scotland (Edinburgh).
Douglas