Registration of Marriages (Ireland) Act, 1863

Persons unable to write may sign by making a cross.

12. In case of the inability to write of any person whose signature is required or necessary under this Act, it shall be lawful for such person to make such signature by making a cross or other mark, which shall be made in the presence of the clergyman or two witnesses, who shall attest the same; and such mark shall be in all respects as binding and effectual as the signature of such person, if capable of writing, would have been.