Complex sentence: At the time of the 1841 census the population was 2,122 but by the 1851 census the population had decreased to 1,454 This is due to The Great Famine, the population decline continued in line with the national trend for emigration throughout the 19th and 20th centuries.
Split into simpler sentences: At the time of the 1841 census the population was 2,122 but by the 1851 census the population had decreased to 1,454 due to The Great Famine. The population decline continued in line with the national trend for emigration throughout the 19th and 20th centuries.