Murchison wrote to all staff on 1st December 1855 explaining that every one-inch geological sheet should be accompanied by an explanatory memoir. The first Irish memoir was for sheet 45SE (later redesignated as sheet 166) covering southern County Tipperary and north west County Waterford. Early memoirs came out with the title 'Data and descriptions', by 1859 they were entitled 'Explanations' and consisted of about 40 pages. Print runs were very low normally about 250.