The British hill-forts, the remarkable vitrified forts of Scotland, and the larger strongholds of the British aborigines, such as the ingenious circumvallations of the White Caterthun overlooking the valley of Strathmore, all derive their peculiar character from the mountainous features of the country; while on the low ground, under the shadow of the Ochils, the elaborate earthworks of the Camp of Ardoch show the strikingly contrasting castrametation of the Roman invaders. The ancient raths of Ireland, which abound in the level districts of that country, as well as on heights where stone is not readily accessible, also furnish highly interesting illustrations of earthworks with a special character derived from the features of their localities. An earthen _dune_ or _rath_, as in the celebrated Rath Keltair at Downpatrick, occupies a commanding site, where it is strongly entrenched, with a considerable space of ground enclosed within its outworks. The celebrated Hill of Tara, in the county of Meath, ceased, according to tradition, to be the chief seat of the Irish kings, since its desertion in the latter part of the sixth century, shortly after the death of Dermot, the son of Fergus. It appears to have been a fortified city; and now, after the devastations of thirteen centuries, its dunes, circumvallations and trenches, present many interesting points of comparison with the more extensive earthworks of the Mississippi valley. But neither the Scottish White Caterthun, nor the Irish Bath Keltair, or even the Rath Righ of Tara Hill, can compare with the remarkable American stronghold of Fort Hill, Ohio, or Fort Ancient on the Little Miami River, in the same State.