I am struggling a bit to verify the information you have provided. I found the marriage of Patrick Smyth and Ellen McNamara on 27.4.1865 at the RC chapel in Ballyphilip, Portaferry. Patrick’s age makes him born c 1840.
There are several trees on Ancestry that list this family. Most seem to give Patrick’s place of birth and death as Waterford, though elsewhere in the trees it gives Newcastle, Co Down for both. And though the couple had a long list of children, I don’t see a Catherine. I also looked for a Patrick Smyth born in Waterford in 1840 living in Co Down in the 1901 & 1911 censuses but failed to find one.
I’d like to check this tree back stage by stage to ensure it’s accurate. So can you tell me where and when Elizabeth Augusta Smyth was born; where and when her parents (Henry & Catherine Smyth) were married, and where & when you think Catherine Smyth was born. That should enable me to try and research the family more easily.