Down Survey

[1] At the time of its creation, it was considered one of the most accurate maps, and the first British imperial survey of an entire conquered nation.

In August 1649, the New Model Army, led by Oliver Cromwell, went to Ireland to re-occupy the country following the Irish Rebellion of 1641.

This army was raised and supported by money advanced by private individuals, subscribed on the security of 2,500,000 acres (10,000 km2) of Irish land to be confiscated at the close of the rebellion.

The Act for the Settlement of Ireland 1652 provided for the confiscation and re-distribution of the lands of the defeated Irish, mostly Confederate Catholics, who had opposed Cromwell and supported the royalists.

Parliamentarian soldiers who served in Ireland were entitled to an allotment of confiscated land there, in lieu of their wages, which the Parliament was unable to pay in full.

[3] William Petty, then physician-general to the Irish armies, on a leave of absence from his position as Professor of Anatomy at Brasenose College, Oxford offered to undertake a new survey which would be concluded quickly – within thirteen months, more cheaply than the surveyor-general's proposals, and with a general map of the country.

The survey employed about a thousand men and was performed with the promised rapidity, not by introducing new scientific methods, but by careful direction of the numerous subordinates among whom the labour was apportioned.

To enable unskilled soldiers to complete the task properly, Petty designed and built some simple instruments.

This land survey method was used widely in rural Ireland up to the nineteenth century and sorting out the precise details was left usually to the legal profession.

[citation needed] Profitable and unprofitable land were distinguished, and there were abbreviated captions for arable, meadow, bog, woodland, mountain and several kinds of pasture, with area figures for each of these categories.

Petty's other requests were reserved for consideration, and only after a delay of more than six months were his sureties released, and his claim for pay acknowledged.

This pamphlet was followed, in 1660, by an essay, Reflections upon some persons and things in Ireland, where he explained that he had defected from the ranks of scientists to do the survey "to demonstrate to the public the utility of a scientific training".

It was the first British imperial survey of an entire conquered nation and Petty was given great credit as a pioneer by the Royal Society.

Considering the time and circumstances in which these maps were executed, their accuracy is surprising, and they continue to be referred to as trustworthy evidence in courts of law even at the present day.

The National Library of Ireland holds a set of Down Survey parish maps copied by Daniel O'Brien in the 1780s and purchased in the 1960s from a firm of Dublin solicitors.