High in the Ox Mountains above Skreen in west Sligo lies a small lake called Lough Achree — Loch an Chroidhe, the lake of the heart. It is popularly the youngest natural lake in Ireland. Gertrude O’Reilly’s retelling of the local tale dates it to 1490, the year the Annals of the Four Masters record an earthquake and a new lake on Sliabh Gamh. The oral version taken down by Templeboy schoolchildren in the 1930s gives no date at all, so the date may be O’Reilly’s own link to the annals. This page holds the records side by side.

The country above Skreen is deep inside Ó Dubhda heartland. Close by, at Dunflin near Skreen, the clan’s hereditary historian Dubhaltach Mac Firbis was murdered in January 1671 — an incident which also sits on the boundary between documented history and local memory. Folklore and record cross here, and keep crossing.

I.  The folk-tale

Gertrude O’Reilly’s retelling of the local story is the fullest printed version. In her words:

“In the year 1490 a farmer in that area owned a spirited stallion and one evening the animal broke away and galloped over the mountains. Unable to catch him, the farmer returned home, as darkness was descending. That night, a terrible storm broke and there was deep rumbling in the mountains. Next morning when the storm abated, the farmer set out to look for his stallion. He came to the place where a small village settlement should be at the foot of a sheer mountain cliff. Instead, he found an expanse of water surrounded by broken boulders. Floating on the lake he found the heart and entrails of the stallion. And so it was called Loch an Chroidhe.”

— Gertrude O’Reilly Mac Hale, O’Dowda Country Stories (2018), Ch 20, p. 98.

O’Reilly adds that on a modern visit the lake was “dark and sinister looking with a sulphurous smell, but set amidst the most glorious scenery overlooking Sligo Bay.”

A shorter version was written down for the Schools’ Collection in the 1930s: a man struck his horse with the bridle at the lake’s edge, the horse kicked him into the water, and “after some time his heart was seen floating on the water, and it is called Loch a Chroidhe ever since.” (Schools’ Collection, vol. 0169, p. 156)

II.  The chronicle entry

The Annals of the Four Masters — compiled in the 1630s from much older materials — record an event in the same year and the same mountain range. The entry is short, administrative, and specific:

“There was an earthquake at Sliabh Gamh, by which a hundred persons were destroyed, among whom was the son of Manus Crossagh O’Hara. Many horses and cows were also killed by it, and much putrid fish was thrown up; and a lake, in which fish is now caught, sprang up in the place.”

— Annala Ríoghachta Éireann (Annals of the Four Masters), M1490.39.

Sliabh Gamh = the Ox Mountains. Sliabh Gamh is the Irish name for the Ox Mountains. The O’Haras held territory on the eastern side of the range; the son of Manus Crossagh named here was a ruling family member. “Putrid fish” and the sudden appearance of a lake where fish can now be caught sit closely beside O’Reilly’s sulphurous water and drowned village.

III.  Where folklore and record meet

Read together, O’Reilly’s tale and the annal entry line up closely:

• Year: 1490 in the annal; 1490 in O’Reilly’s telling, though not in the oral version recorded in the 1930s.
• Place: the Ox Mountains, in both.
• Physical signature: a new lake where the ground had been, with a sulphurous or “putrid” quality, in both.
• Casualties: in the folk-tale, a stallion and a vanished village; in the Annals, a hundred persons, one of them named, the son of a ruling family, and many cattle.

What the geology suggests. Whatever the mechanism — a heavy seismic event, a saturation-and-collapse of peat and scree, a sudden hillside failure after heavy rain — something happened at Sliabh Gamh in 1490, and it left both a lake and a story. The annal kept the date and the death toll; the folk-tale kept the horse and the heart that gave the lake its name.

IV.  A wider Irish pattern

Drowned-village legends are a recognised feature of Irish folk-tradition. The most famous is Lough Neagh, said to have flooded overnight when a careless hand left a magic well uncovered; a stone round tower can still be seen beneath its waters in some tellings. Lough Gur in Limerick has its own version. What makes Lough Achree distinct is that the principal national annals record a lake appearing in these mountains in 1490, a written witness most drowned-land legends lack.

V.  The Ó Dubhda tie

Skreen and the Ox Mountains are in the heart of Tireragh, Ó Dubhda country. Close by, at Dunflin, Dubhaltach Mac Firbis, the last hereditary historian of the clan and compiler of Leabhar Mór na nGenealach, was murdered in 1671. The same landscape holds the clan’s oldest foundation stories (see Ancient and Sacred Sites) and its final scholarly voice. Lough Achree is not an Ó Dubhda site in any narrow sense; it is a place where the people who carried these stories lived and walked.