Ordanance Survey Letter Mayo, by Michael Herity . MRIA. Editor.

Edited & introduced by Proffesor Michael Herity MRIA, This is hugely important to Irelands history. John O`Donovan began his massive work in Ballina Mayo with Thomas O`conor in 1838 by 1841 all the Countys of Ireland had been covered. This edition is copied from the original letters in the Royal Irish Academy Library. Multiple signed or not copies are available.