" It is a remarkably plain statement of importance for something that has since slipped so thoroughly from public consciousness. The channel in question was no minor ditch; it was a working artery of the medieval city, carrying fresh water to streets and households at a time when such infrastructure was genuinely a matter of survival.

The Down Survey, carried out between 1655 and 1656 under the direction of William Petty, was a systematic mapping of Irish land intended primarily to facilitate the redistribution of confiscated property following the Cromwellian conquest. That this watercourse appeared on those maps, named so explicitly, suggests it was considered a landmark feature of the landscape rather than a mere incidental detail. By 1837, when the Ordnance Survey produced its six-inch maps of Ireland, the same feature was recorded under two related labels: "Millrace" and "Watercourse." The shift in terminology is telling. A millrace is the channel that directs water to power a mill wheel, suggesting the flow had acquired an industrial function alongside its original civic one. According to John Joyce's 1912 account of Dublin's streets and their histories, this channel formed part of the eastern branch of the medieval Dublin watercourse, the system that fed Deane Street among other parts of the city.

The physical trace of this watercourse is not something a visitor is likely to encounter as a dramatic ruin or a preserved monument. Dublin's south city has been built over and rebuilt across many centuries, and the channel now exists primarily as a cartographic and documentary record rather than a visible feature on the ground. Anyone with an interest in the archaeology of urban water systems might approach it by overlaying the 1837 OS six-inch mapping, freely available through the tailte.ie geoportal, onto a modern street map of the area. The exercise reveals how the logic of the medieval city, shaped by the need to move water efficiently from source to settlement, still haunts the alignments of streets and property boundaries long after the water itself disappeared underground.