The worked oak timbers they unearthed, including the parts of a wooden trough and the floor of a dam, belonged to a horizontal-wheeled mill, a type of early medieval grain-processing technology in which water was directed through a narrow channel onto paddles fitted horizontally beneath a millstone, spinning it directly without the need for gearing. The discovery was recorded by Robertson in 1861 and later discussed by Lucas in 1953, but the site itself had long since been buried under the infrastructure of a growing nineteenth-century city.

The mill had been fed by a spring locally known in the nineteenth century as the Seven Springs, roughly 760 metres south-east of Kilkenny Castle. Dendrochronology, the science of dating timber by analysing its annual growth rings, subsequently placed the wooden trough in the eighth century. That dating places the mill firmly within the early medieval period and suggests a connection to Domhnach Mór, an ecclesiastical settlement associated with St Patrick's, which lay approximately 790 metres to the west. Domhnach Mór-type place names in Ireland generally point to early Christian foundations, and a mill attached to such a settlement would have been entirely typical; monastic communities of the period were known to operate mills as part of their agricultural economy, grinding grain for the community and sometimes for the surrounding population. The Seven Springs that once powered it have left no obvious trace in the present landscape, absorbed into the city's water management long ago.