Hi,
I had a look at the version of Cantwell's Memorials but I couldn't find a Thomas Leary that was the right match for place or dates. The only Thomas Leary that was a reasonable match date-wise was at the address Ballyvalloo - but I don't think that would be the one you are looking for?
Just in case, though, he was Thomas Leary 1804 - 13.Dec.1856, stone erected by his wife Bridget.
The Learys listed at Ballybrennan Cemetary are:
"Erected by the Widow Leary of Killegney in memory of her beloved husband James Leary who departed this life January 25th 1848 aged 72 years, also her daughter Catherine Leary died September 25th 1845 aged 17 years."
"Here lies ye body of James Leary who died July 2nd 1760 aged 55 years."
"Erected by Andrew Leary in memory of his mother Mary Leary, late of Clonroche who depd. this life Novr. 1839 aged 56 years, also his brother Richard Leary died March 20th 1853 aged 32."
- I don't know if this is relevant to you, but the first headstone is one of two headstones apparently next to each other on the same kerbed grave, listed in the memorials as an 'A' and a 'B' set. The 'A' headstone is the Leary one; the 'B' headstone belongs to the Mernagh family.
Sorry I couldn't find a listing for Thomas. With regards to Cantwell's Index, I find the same thing when looking for ancestors - some of them are listed and others I can't find.
All the best,
Tamsin