Allison, I'm not sure about Margaret Harriet Montgomery Blackley but I have come accross Jessie Juliet Montgomery Blackley b: 1903 Mirboo, Victoria, d: 20/5/1960 married Fergus Lindsay 24/6/1944 in Brisbane, Qld AU.I have more detailson her parents and syblings back to the 1700's in Scotland.The Montgomery comes from her paternal Grandmother Jannet Montgomery (b: 1783, d: 12/12/1862 cleuchhead, Durisdeer, Dumfrieshire, Scotland), second spouse of John Blackley b: 1764 in Crawford, Laarkshire, Scotland.d: 30/3/1866 at Cleuchhead, Durisdeer, Dumfriesshire, Scotland).
Other possible connections include: Jessie Montgomery Blackley b: 1854 in Dumfries d: 2/1/1930 in Dumfries. The Blackleys that moved from Scotland to Victoria before speading all over Australia (all sons of the John & Jannet mentioned above) include * John Blackley b21/4/1858 d: 10/9/1922 at Tullyvea, Dimboola Victoria AU; * Wiliam Hyslop Blackley (my great Grandfather) and * James Blackley b: 28/9/1863 d: 25/8/1894 Stawell Victoria.
I have traced very few decendents from these original families other than my direcr ancestors. I hope this little bit can help.I'd be interested if you found a connection, Regards Roxane Blackley