Hi. I have spotted your post from back in 1911 regarding Alexander Halley (who married Margaret McKay in 1845).
I have researched Alexander Halley fully, as Margaret McKay was his second wife and he then went on to reside with my 3x gt.aunt whom he claimed to have married in 1856 in Geelong, whilst still married to Margaret McKay.
I have his 2 marriage certificates plus his death certificate which confirms all of the above (his first wife was Isabella Black) and also clearly states his place of birth to be Dunning, Perthshire, Scotland - this is born out in the marriage register for Falkirk, Stirlingshire, Scotland in 1841 when he married Isabella Black, ie Alexander Halley from the parish of Dunning to Isabella Black of this parish, married 3 September 1841 at Falkirk.
Both Alexander Halley and Isabella Black were criminals - Alex was convicted at Edinburgh and Isabella at Stirling Court - both sentenced to transportation to Van Deimen's Land, but Alexander was granted a pardon and sent to Victoria. He married Margaret McKay only 6 weeks after arriving in Australia and then the couple settled in Geelong to have 3 children, Annie, Margaret & Alexander, after which he left Margaret and set up with my 3x gt.aunt Frances Melmer in 1856. The couple then moved to Toowoomba, Queensland where Frances died in 1878 (Alexander registered her death) and he later died in the Benevolent Asylum, Dunwich, Queensland, in 1884. All three wives are clearly stated on his death certificate, a copy of which I have and am happy to share with you if you respond to this message.
Apologies if you already have all this information but I have found no-one, as yet, on the internet who has anywhere near the correct information or research regarding Alexander Halley.
Maybe I will hear back from you. Best regards.