Mary McDonald

[Mutley]

Good morning Elma

My gut feeling is that the two are the same child just a misunderstanding. There is only one Alexander Bain b Penally and that is in March Q 1881. Perhaps the baby had been at the grandmother's house when the census form was filled in. It may even have been born there. I think the age 1 is a mistake.
The other census at the barracks would, I imagine, have been filled in by a senior officer.

The later info you have about Alexander returning and leaving Mary in Ireland is interesting and quite sad isn't it. What did she die of?

I felt the same. I looked at the original thinking the age 1 may have been 1m. It just says 1 but perhaps it was meant to be 1 month.