I recently came across some Nowlan's from Dublin in my family tree. The name is quite popular in Dublin but I found the free information on Irishgeneologie.ie quite good. I had a very quick look for you as I sorted through lots of Nowlans to find mine. I couldn't find Agnes but I found an RC marriage between a John and Margaret Byrne in Rathfarnam, Dublin for 1836? I took a screen shot I'll see if I can attach it for you.