If you go to the British Library website and search for "Parliamentary Constituencies and their Registers since 1832", you can download the revised edition of this work. It includes a summary of extensions to the parliamentary franchise (as does Jeremy Gibson's Electoral Registers 1832–1948). It reveals also that the British Library has scarcely any Irish registers up to 1922 and none for anywhere in Cork. Mr Gibson does not attempt to list pre-1922 Irish registers, so I must leave it to others to say what exists for the place in question. However, just to spread a bit more gloom, I can add that I asked an archivist at the Cork City Archives whether they had anything in the way of rating records or voters' lists for the 1860s. "Not that early," was the answer. Jeremy Wilkes