In a plan-drawing of the siege of Enniskillen castle, in the year 1592, the remains of a crannog appear in the river close to the castle, where seemingly a circle of stakes encloses a diminutive island.[168] The survey or maps of the county Monaghan, made by one Francis Jobson in 1590, though meagre, and certainly--as its designer expresses in an apologetic note to Burghley--“nothing perfect,” is nevertheless highly interesting by reason of the rude sketches of the water-laved abodes of the chiefs of Monaghan. Each barony possessed one, designated “the island”; that in Farney was at _Lisanisk_, written _Lysonske_, and it is marked on the map as “The Island, Ever M’Cooley’s house.” In the year 1843 traces of this structure were discovered; the former artificial island was then a peninsula, having been joined to the shore. Seven feet below the surface of the ground, and two feet below the water level, a double row of piles was disclosed, formed of young trees with the bark still adhering, and from six to twelve inches in diameter; the area thus enclosed was an oval sixty feet by forty-two feet.[169] In Jobson’s map several crannogs are represented in _Lough Mucknoe_, barony of Cremorne; also “Mac Mahoun’s house,” or crannog, is shown in _Lough Monnachin_. According to the same authority, a sub-chief of the present county Monaghan, named Mac Kenna, resided in a crannog either on the lake of _Glaslough_ or that of _Erny_ in the parish of Donagh. The map is so rough that it is difficult to decide which of the lakes is intended. Francis Jobson likewise represents the residence of a chieftain named Brian Mahon, as a crannog on _Lough Rouskey_, in the parish of Killeevan. In 1588 Aedh O’Donnell and nine of his followers were murdered in the crannog of _Mongavlin_, parish of Taughboyne, county Donegal. “The crannog is not now traceable, nor is there any water in the locality in which such a structure could have existed, with the exception of Lough Foyle, on the margin of which Mongavlin is situated.”[170] In 1571 the Mac Dermots burned _Inis-Floinn_ and _Inis-Mic-David_,[171] situated somewhere on the borders of Roscommon and Sligo. The statement that the islands were burned seems to sufficiently demonstrate their artificial character. In the sixteenth century the island fortress of _Inishrush_ was held by an Irish sub-chief named Brian Carragh; and Dr. Reeves quotes a document from the State Paper Office, in which allusion is made to it in the form of a letter to a Captain Piers, dated 10th December, 1566. The writer says:--“Als mony as we migt drywe and dreaf ower ye Ban all ye carycht yt Brean Karriche hade … and ane innyse (i.e. _Island_, namely _Inishrush_), yt Brean Karriche hade of befair and Oneiles servand tuk yt, and now we have gotten ye innys agane, and that harchips I behuffit to Sla yame to be meet to my arme.” The crannog of Inishrush (_i. e._ the island of the wood), or perhaps, peninsula, has long ceased to bear that name. It is a small island in the middle of a marshy basin called Green Lough, in the townland of Inishrush, barony of Loughinsholin, county Derry. Some years ago this marsh was a sheet of water about half a mile in circumference, the drainage of which was effected by means of a deep cut that carried its contents into the Clady river. About the centre of the lakelet was a circular artificial mound composed of clay and gravel, the sides gradually shelving downwards. It was girt with a circle--about one hundred and fifty feet in circumference--of oak piles, most of them still in position. Horizontal beams of oak were mortised in the upper ends, and upon this framework rested seemingly the foundation of a wooden house securely attached to the supporting timbers. An artificial causeway, leading from the western margin of the lough, appears to have formerly connected the crannog with terra firma. The sole discovery made was a fragment of chain-armour. The lake basin became again partly submerged owing to neglect of the drainage, and when Dr. Reeves visited the locality in 1859, he failed to reach the crannog. It remained, however, above water, prominently covered with a luxuriant growth of grass.[172]