Richard Griffith (b. Dublin 1784) had already established himself as a distinguished geologist and inspector of Irish mines when, in 1825, he was chosen to be Ireland's Boundary Surveyor. Griffith's appointment coincided with the government's determination to achieve a uniform system of land measuring and valuing for the purpose of eliminating various inequities in levying the two main forms of local taxation in Ireland, the tithe and the county cess, at the townland level. As the head of the Boundary Department of Ireland, Griffith would spend the next forty years supervising land valuation in Ireland and, in particular, the great Ordnance Survey of Irish townlands which fixed local boundaries throughout the nation. The Ordnance Survey documents, comprising over 3,000 maps and 2,300 registers, and Griffith's valuations of 1826, 1846, and 1852, were the surviving products of Griffith's efforts, and they constitute perhaps the greatest sources in all of Irish genealogy. The content has been divided into two parts. The first half of the volume treats the history and method used by Griffith and his colleagues in producing the valuations. Here Reilly explains how the surveys were conducted, how standard Irish forms of townland names were assigned, how the descriptive Ordnance Survey Memoirs were compiled, and what one can expect to find within their rich contents. In separate chapters devoted to the three valuations, Reilly describes, among other things, how the valuators assigned a value to property, how the information was publicized, and the relationship of the valuations to the new Irish Poor Laws. Facsimile illustrations of maps, memoirs and other documents from the valuations abound here as they do in the second half of the work, a discussion of Griffith's genealogical importance.