_Island M’Coo_ is one hundred and eighty yards from the nearest shore. It seemed to be surrounded by a circle of piles thirty-five feet in diameter, and in a season of low water _gun-barrels_ and _bronze spear-heads_ were said to have been brought up in the prongs of eel-spears. The incongruity of the juxta-position of gun-barrels and bronze spear-heads can easily be explained. In the year 1798 all the guns seized throughout the surrounding country were brought into the town of Loughrea, and the magistrate in charge, having orders to destroy them, caused them to be carried out and sunk in the lake. At the east side of the island were observed traces of four canoes with their prows turned towards the shore. An attempt to raise one of them--a single-piece canoe of oak--failed, it being so decomposed that it broke across in the middle. The age of these crannogs was estimated to be over 1800 years, or before the Christian era. When they were first constructed the surface of the lake must have been at least seven feet lower, and at a subsequent period the west part of the lake must have been twelve feet deeper. The change in the level of the water was caused by the silting up of its outlet. The ancient stream from the lake seems to have been at the west end of the town of Loughrea, where is an alluvial deposit; whilst at its modern outlet there is strong corn gravel, and a little below its present bed there seems to be rock. The town is more than four hundred years old, and since that date the water could scarcely have changed its level, because the eastern outlet of the lake ran at the foot of the town wall; and thus forming part of the town defences, the inhabitants would have kept the stream free.[248] _Crannog Mac Navin._--_Ante_, pp. 149-50. _Ballinafad._--_Ante_, p. 24. _Ballinahinch._--Ante, p. 34. _Caislen-na-Caillighe._--_Ante_, pp. 33-4. _Goromna Island._--Ante, p. 33. _Lough Bola._--_Ante_, p. 34. _Lough Cam._--Ante, p. 34. _Lough Hackett_, formerly _Lough Cimbe_ (pronounced Kimmay), _ante_, p. 157.--An allusion that, in all probability, refers to a siege of this crannog, occurs in the _Annals_ of Lough Cé, under date A.D. 1067, where it is stated that Torlogh O’Brien led “a hosting to Loch-Cime.” COUNTY MAYO. [Illustration: Fig. 226.--General view of the Crannog of Loughannaderriga, Achill Island.]