For two research fellows at the Institute of Irish Studies at Queen's University, Belfast, editing the Ordnance Survey Memoirs of Ireland has been a labour of love. This month, the 40th and last volume of memoirs - which examines Counties Cavan, Leitrim, Louth, Monaghan and Sligo between 1834-38 - is being published.

The editors, Angeligue Day and Patrick McWilliams, breath sighs of relief tinged with sadness. For them, the have become a way of life.

It all began back in 1824 when the Duke of Wellington, prime minister at the time, authorised the first ordnance survey of Ireland to facilitate a uniform system of property valuation for taxation purposes. Colonel Thomas Colby, who had under his command officers of the Royal Engineers and three companies of sappers and miners, was appointed director of the survey.

His representative in Ireland was Lieutenant Thomas Larcom, who, say Day and McWilliams, is one of the great unsung heroes of Ireland. He was "a remarkable man" and an "altruistic friend of Ireland." Later he became Under-Secretary of State for Ireland and donated his papers to the National Library.

It was Larcom who directed his officers to report on a range of issues including topics of social and economic interest. Often local civilians were recruited as information gatherers. Larcom's intention was to provide the government with a picture of Ireland which would help it legislate for improvements.

"It was incredible that the project was ever undertaken and it was made possible only by Larcom's interest," notes Day. "He was interested in the demographic spread long before anyone else."

Over the years, hundreds of local people were employed on the survey and it was considered prestigious work. Thomas Fagan, a teacher and sometime tax collector from Limavaddy, Co Derry, was a local hero. An Irish speaker, he mixed with the populace and wrote his contributions to the in a vernacular style.

John O'Donovan, QUB's first professor of Celtic studies, "cut his teeth on the survey" and was responsible for many of the place-names, according to McWilliams.

Both researchers reject the view that the survey was used to suppress Irish culture, as has often been argued. The survey preserved many names which would have disappeared due to the Famine and the subsequent pressure on land, which caused antiquities to be cleared away. Indeed, research into Irish place-names has been enhanced by the survey, they say.

The provide a snapshot view of Ireland before the Famine. "Such local detail is unique in the whole of Europe," observes Day. "The Irish people involved in the survey unearthed a lot of local knowledge." Information gatherers were encouraged to contribute details of local family history, local traditions and ways of life, local commerce and land use. Included is invaluable information on gardening, sport, education and even interior decoration.

Patrick McWilliams notes the cheerfulness of the people in times of grinding poverty. "The Memoirs have taught me to read between the lines," he says, "and be aware of the prejudices of some of the people who wrote them." For example, they write disparagingly about the smell of dung - "but this could also be interpreted as a sign of wealth. They talk of people living promiscuously together, but poverty and a shortage of land and housing were the causes."

Although the note the decline of Irish, it reveals that in Limavaddy Protestant English-speaking merchants were forced to learn Irish in order to do business in the markets. There are innumerable references, too, to the drunkeness of the population, both Catholic and Protestant. The manuscripts were all handwritten, often in almost indecipherable or faded script. Angelique Day has read through some 22,000 sheets of manuscript since she first began cataloguing the papers in 1981. Today, the published version amounts to 4,500 printed pages containing over 100,000 words in 40 volumes.

Originally it had been intended that the ordnance survey would cover the whole of Ireland, but sadly the money ran out in 1839. It was Sir Robert Peel's government which finally pulled the plug and refused further financing, despite a parliamentary commission favouring its continuation.

"The Memoirs," says Day, "allowed people to study their own past and there was a huge outcry when it ceased." Nonetheless, we're left with fascinating, 19th century Domesday-Book accounts of life in Antrim, Armagh, Donegal, Down, Fermanagh, Derry, Tyrone, Cavan, Leitrim, Louth, Monaghan and Sligo.

Ordnance Survey Memoirs of Ireland - 1830-1840 is edited by Angelique Day and Patrick McWilliams and published by the Institute of Irish Studies, QUB. Volumes 1-18 £15stg (hardback), £7.50 stg (paperback). Volumes 19-40 £18stg (hardback), £8.75stg (paperback).