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 produced it being in constant operation, it remains undiminished. Along the line of the Vir two seas meet at right angles, and the result is the formation of a ridge running in a diagonal between the lines of force. The sound here is called Vaarasound. The word Vir appears to be the prefix in the place-name Virkie, in Dunrossness, and of the ancient earthwork in the Blue Mull already referred to.

On the mainland of Unst, half a mile south from the Holm, there is another very extensive broch called the Overbrough, consisting of a central tower with two concentric walls or embankments about 20 feet apart. From this ancient fort a very wide view can be obtained, both seaward and landward. The sentinel on its watch-tower could signal to no fewer than seven brochs, viz.:. Brough Holm; Brough of North Yell; Snaabrough, Oganess, and Musselbrough, in Unst; Strandiebrough and Brough Lodge, in Fetlar.

Regarding the brochs in the district of