Marriage of John Armit Esquire to Eliza Gifford of Fitzwilliam Street, Dublin 8 Aug. 1822 - seewww.irishgenealogy.ie
no record of John Henry
In Dublin Will and Grant Books Diocese of Dublin
Deputy Keeper of Public Records:
a Marriage Licence for the above 1822
Cantwell Memorials show a death for a John Armit, Church of Ireland, St. Patrick's. I can look this up later. Some gravestone inscriptions have lots of family information but not always.
The 1824 Pigot's Directory under Dublin Nobility:
W.J. Armit Esquire, 36 Blessington Street, Dublin
Was unable to locate the above in the 1846 Slater's Directory.
Have you tried the Registery of Deeds-Ireland? just google its a "freepagesrootsweb page"
MILGENIRE, google - is a military page for Military Genealogy in Ireland, they sometimes have enlistment papers with parents names.
There is a William Armit in the 1871 UK Census which identifies irish born persons, a nephew age 33, Notthingham.