None of the writers on Irish crannogs appear to have paid much attention to the structure of these islands, and beyond the mere statement that they were "stockaded," palisaded, or surrounded by one or more circles of piles, they give no explanation of the attachments and proper function of the surrounding piles. These are generally described as having been driven into the muddy bottom of the lake, and the most essential part of the mechanism of construction, viz., the horizontal mortised beams, has been only incidentally noticed. Though the purpose of these horizontal beams does not appear to have been understood, it is of importance to observe that their existence has not been entirely overlooked, as will be seen from the following quotations. In his description of the crannog at Lagore near Dunshaughlin, Sir W. R. Wilde says: "The circumference of the circle was formed by upright posts of black oak, measuring from 6 to 8 feet in height; these were mortised into beams of a similar material laid flat upon the marl and sand beneath the bog, and nearly 16 feet below the present surface. The upright posts were held together by connecting cross-beams, and (said to be) fastened by large iron nails; parts of a second upper tier of posts were likewise found resting on the lower ones. The space thus enclosed was divided into separate compartments by septa or divisions that intersected each other in different directions; these were also formed of oaken beams in a state of good preservation, joined together with greater accuracy than the former, and in some cases having their sides grooved or rabbeted to admit large panels, driven down between them."[3] Dr. Reeves, writing about a crannog in the county of Antrim, says: "These piles were from 17 to 20 feet long, and from 6 to 8 inches thick, driven into the bed of the lough, and projecting above this bed about 5 or 6 feet. They were bound together at the top by horizontal oak beams, into which they were mortised, and secured in the mortise by stout wooden pegs."[4] My next quotation is from a paper by G. H. Kinahan, Esq., of the Geological Survey of Ireland, on Crannogs in Lough Rea: "A little N.W. of the double row, in the old working, there is a part of a circle of piles; and in another, a row of piles running nearly E. and W. Mr. Hemsworth of Danesfort, who spent many of his younger days boating on the lake, and knows every part of it, informs me that on the upper end of some of the upright piles there were the marks of where horizontal beams were mortised on them. These seemed now to have disappeared, as I did not remark them."[5]