The definition of this territory which best suits the purposes of history, and in all respects most nearly accords with those of political and social geography, is one which makes it commensurate with the country or locations of the ancient Highland clans. This definition assigns to the Highlands all the continental territory north of the Moray frith, and all the territory, both insular and continental, westward of an easily traceable line from that frith to the frith of Clyde. The line commences at the mouth of the river Nairn: thence, with the exception of a slight north-eastward or outward curve, the central point of which is on the river Spey, it runs due south-east till it strikes the river Dee at Tullach, nearly on the third degree of longitude west of Greenwich; it then runs generally south till it falls upon Westwater, or the southern large head-water of the North Esk; thence, over a long stretch, it runs almost due south-west, and with scarcely a deviation, till it falls upon the Clyde at Ardmore in the parish of Cardross; and now onward to the Atlantic ocean, it moves along the frith of Clyde, keeping near to the continent, and excluding none of the Clyde islands except the comparatively unimportant Cumbraes. All the Scottish territory west and north-west of this line is properly the Highlands. Yet both for the convenience of topographical description, and because, altogether down to the middle of the 13th century, and partially down to the middle of the 16th, the Highlands and the Western Islands were politically and historically distinct regions, the latter are usually viewed apart under the name of the Hebrides. The mainland Highlands, or the Highlands after the Hebrides are deducted, extend in extreme length from Duncansby Head, or John o’ Groat’s on the north, to the Mull of Kintyre on the south, about 250 miles; but over a distance of 90 miles at the northern end, they have an average breadth of only about 45 miles,--over a distance of 50 or 55 miles at the southern end, they consist mainly of the Clyde islands, and the very narrow peninsula of Kintyre,--and even at their broadest part, from the eastern base of the Grampians to Ardnamurchan Point on the west, they do not extend to more than 120 miles. The district comprehends the whole of the counties of Caithness, Sutherland, Ross, Cromarty, Inverness, and Argyle, large parts of Nairn, Perth, Dumbarton, and Bute, and considerable portions of Elgin, Banff, Aberdeen, Forfar, and Stirling. Considerable parts of this district, however, such as Caithness-shire, the island of Bute, and some large tracts of moor or valley or flanking plain, do not exhibit the physical features which are strictly Highland.