Going back to your first post about the Tolbooth Church.
Before the current (now disused) church was built, the Tolbooth Church seems to have been the western most church contained within St Giles. This building was divided into three churches to serve three separate parts of the Old Town. The part dedicated to serve as the Tolbooth Church was nearest to the Tolbooth itself. The Tolbooth was known as the Heart of Midlothian (no, not the footie club

) and was demolished in 1817. St Giles is of course still there and now undivided.
There is a 19th century book on the Tolbooth Church:
http://www.archive.org/details/cu31924029475898Engraving of the Tolbooth outside St Giles:
http://www.edinphoto.org.uk/0_eng_one/0_engraving_-_one_1_133_old_tolbooth.htmMoving on to your later posts- I'm a tad concerned that Agnes apparently married in 1717, aged 14. While it was legal, it is not common.
You say that Miriam/Mary/May must have been Edinburgh local to meet a naval person. I think I'd be a little cautious. I don't think of Edinburgh as particularly associated with the Royal Navy or the Marines. I know Smith is a pain of a name to search for (similar to John Brown in many ways

), but not impossible. It does mean that caution is really important. Work backwards to link the generations, otherwise it can lead to difficulties.
Nell