A Janet Bowie/McGilvary (as indexed on SP) died in Milton in 1876, with a birth year of 1823 which would fit for your Charles' mother.
Monica
Checked out the death certificate of Janet McGilvray (spelt as McGilvary on the cert.) - no wonder I had trouble tracking stuff down with so many variations of the spelling lol.
She died aged 53 (b. 1823) on the 15 Jan 1876 wife of Charles McGilvary (sic) who is by now a Flour Mill Labourer and not a Blacksmith and interestingly enough her parents are listed as Duncan Bowie (Fisherman) and Janet Bowie (Brown) both deceased.
Still cant understand why the name Campbell appeared as her maiden name on her sons wedding certificate only 2 months later on 31 Mar 1876
George