p52.
For details on the potato diet, see Cecil Woodham-Smith (1962), The Great Hunger, pp 30–31. The 1779 population figure is taken from Arthur Young’s Tour In Ireland (1776–1779): “The common idea is, that there are something under three millions in Ireland”, available at http://tinyurl.com/pyfdhfr . This is a less reliable estimate than the census figure, but nonetheless plausible.