He was deeply involved in Daniel O'Connell's Catholic Emancipation movement and in relief work among the poor of County Kilkenny. He was also an avid bird watcher and a collector of rare manuscripts in the Irish language.
His diary, the Cín Lae Amhlaoibh, was kept between 1827 and 1835. It remains one of the most important sources for 19th century Irish life and one of the only surviving works from the perspective of the peasantry.
"27 June, 1827 ...I saw two water wagtails hopping and flitting within a yard of a cat which was crossing the road. They were noisily mocking the cat, which kept glancing from one side to the other at them. The poor man does the same to the tyrant when he gets the opportunity - just as the birds do to the cat.
"29 June, 1827 ...Feast of Saint Peter and Paul. A holiday... Hurling on the Fair Green. It was a good game. The sticks were being brandished like swords. Hurling is a war-like game. The west side won the first match and the east the second. You could hear the sticks striking the ball from one end of the Green to the other. I was watching from the top end myself with Doctor Céatinn and two priests. The well-to-do young men and women were strolling up and down the Green and on the level causeway in the center.
"16 August, 1827 ...At ten o'clock this morning my mother Máire Ní Bhuachalla Ní Shúilleabháin, wife of DOnncha Ó Súilleabháin, died after receiving Extreme Unction by the Grace of Amighty God. She was close to eighty years of age. Her husband, my father, died in the Year of Christ 1808, the year of the big snow. He was buried in Cill Bhríde, beside Áth an Iúir a mile from Callan, although his family's burial place is Iríolach Monastery at Mucros beside Loch Léin in Killarney, Co. Kerry. But the pressures of life sent us a long way from our people, sixteen and twenty years ago... Small boys and girls are coming home with little bundles of gleanings.
"February 3, 1828 ...There is a lonely path near Uisce Dun and Móinteán na Cisi which is called the Mass Boreen. The name comes from the time when the Catholic Church was persecuted in Ireland, and Mass had to be said in woods and on moors, on wattled places in bogs, and in caves. But as the proverb says, It is better to look forward with one eye than to look backwards with two...
"8 May, 1830 ...There is a large underground cave in Baile na Síg, two miles west of Callan, which is called 'The Rapparee's Hole.' It seems they used to hide there after Cromwell's and King William's time. It's many the fine, good, honest man who had been reared in luxury and happiness who was reduced to robbery, begging, or exile by those two Englishmen.
"September 11, 1830 ...Last Thursday in Dublin Castle I heard a band playing music which was like the music of Devils. The bassoons were like a sow crooning to her young. The musical pipe sounded like the squeeling of piglets. The flute sounded like a muffled fart, the trumpets and French horns sounded like the laughter of fiends and the serpent like the sighing of demons, the trombone like the harsh cry of the heron. It wasn't soft like the lovenote of the heron. The clarinets were like the cry of the plover and the corncrake. It in no way resembled the sweet, gently moving music of the Irish.