Sandy
That is interesting to hear that the owner of Birkhill house at that time may have been a doctor, because other than at a Church, it would make sense at that time to leave a foundling at a Doctor's house.
I think being found at Birkhill explains the "Birkhill" part of her name, but of course that leaves the "Mcalpine" part....unless she was adopted by a family called Mcalpine, or even married/lived with someone called Mcalpine before she married Robert Stevenson. I can't think of any other reasons for the name "Mcalpine" to appear on documents. Even though it is the end of the line searching for her forebears, there may still be wee snippets of facts which can round out her life.
Thanks for that info. I'll do a wee bit of research on Birkhill House and the families who lived there, just for "background". It's amazing how often "gut feeling" can help researching ancestors (as long as you don't go down the wrong family line as a result of not making certain of your facts)