I've had more than a few requests for this over the years so, while I had some time today, I scanned Nora Chadwick's Geilt article and have posted it as a PDF that you can download at this link.
While the article was originally published in 1942, it covers a lot of ground regarding these figures in Gaelic mythology. It's an important work for anyone interested in the mad poet figure in Gaelic texts and has been very helpful in my research and work over the years. If you're interested in reading Buile Suibhne, this will help with understanding the background and context in which this and other geilt tales were written.
Since I posted her Imbas Forosnai article here some months ago, it seemed fitting to post this companion piece. I hope you'll find them useful!
Oh, and blessed Imbolc!