The geological formation consists chiefly of sandstone, sandstone flag, and occasionally limestone; but granite and gneiss are also found in the west. On the east Caithness presents a precipitous coast, with scarcely a creek in which a vessel, even of small size, can find shelter. On the northern coast, where the Pentland Firth separates it from the Orkney islands, stand at the distance of 13 miles from each other the two bold headlands of Duncansby Head on the north-east and Dunnet Head on the north-west. The latter, the most northern point of Scotland, is situated in 58° 40' N. lat. and 3° 21' W. long., and is crowned by a lighthouse, with a fixed light, built on the rock 346 feet above the level of the sea; while the former is marked by the white steeple of Cannisby on the west. The navigation of the Pentland Firth is attended with considerable danger, from the strength and eddies of the current. Off the island of Stroma, which is separated from the mainland by a strait three miles broad, is a small vortex called the Swalchie; while nearer the shore are the “Merry Men of Mey,” a group of breakers caused by eddies between projecting headlands. On the east coast, in addition to the harbour of Wick, erected in 1831, at a cost of above £40,000, and since improved at further expense, there is a small harbour at Sarclett and another at Staxigoe, a small pier at Clyth and another at Lybster. On the northern coast Scrabster roads in Thurso Bay afford tolerably good anchorage, while at Thurso and Sandside Bay are commodious harbours for larger vessels.

The climate of Caithness is variable, but not unhealthy; and though the winter storms fall with great severity on the unsheltered coast, yet from its proximity to a large expanse of sea the cold is not intense and snow seldom lies many days continuously. In winter and spring the northern shore is subject to frequent and disastrous gales from the N. and N.W. The waters of Forss, Thurso, and Wick, are the principal streams which traverse the county, but none of them are of any particular importance. The largest lochs are those of Watten and Cathel; there are numerous small ones well stocked with trout.

A great change has been effected in the agricultural position of Caithness, chiefly by the late James Traill, Esq. of Ratter. The farms along the coast are still mostly in the hands of small farmers, who cultivate the soil only during the intervals of the fishing-season; but inland, in the more elevated districts, and along the banks of the principal streams, the land is let out into large farms, with leases long enough to encourage the holder to improve the soil and practise a rotation of crops. The average extent of land held by each occupier, in 1874, was 39 acres, much larger than the average in Sutherlandshire, which only amounted to 10 acres in the same year. In the pasturage ground, black cattle and sheep, chiefly of the Leicester and Cheviot breeds, are reared for the southern markets; and, independently of the weekly corn-markets at Thurso and Wick, the rapidity of communication with the south is opening up a valuable market for the produce of the dairy and farmyard.

The principal crops raised are oats, beans, potatoes, and turnips; wheat can be grown only where draining has been carried to considerable perfection. In 1874 there were only 87 acres in wheat, 1895 in barley, 70 in rye, and 27 in peas; while oats occupied 33,071 acres, turnips 14,045, and potatoes 2190. In the same year there were 21,567 acres in permanent pasture, and 6222 in temporary grass, while only 440 were covered with wood. The number of cattle of all kinds in the county was 22,616, sheep 108,829, horses 4969, and pigs 1789. But the great source of profit to the inhabitants is to be found in the fisheries of cod, ling, lobsters, and herring, which abound all around the coast. The most important is the herring-fishery, though it has considerably lessened in value during the last twenty or thirty years. Beginning about the end of July the season lasts for about six weeks, the centre of operations being at Wick and the surrounding districts. The number of fishermen employed in 1874 was 4304; and the value of boats, nets, lines, <fcc., for the same year, was estimated at £112,270. Besides those more immediately engaged in manning the boats, the fisheries give employment to a large number of coopers, curers, packers, and others. The salmon-fisheries on the coast and at the mouths of rivers were formerly very productive, and are still let at high prices. At intervals along the coast are valuable quarries of freestone and slate, and of excellent flag for pavements; but the county is far from rich in other minerals. Slight traces of lead and iron have been found in the mountainous districts; and indications of coal, or rather of bituminous shale, have been noticed at Cannisby. The only article of manufacture is woollen cloth. The Highland Railway, opened in 1873, enters the county from Sutherlandshire, and curves through the centre to Wick, passing Altnabreac, Scotscalder, Halkirk, Georgemas, Bower, Watten, and Bilbster; while a branch line runs from the Georgemas junction to Thurso.

The early history of Caithness may, to some extent, be traced in the various character of the remains and the diversity of its local nomenclature. Picts’ houses, Norwegian names, and Danish mounds attest that the Celts were successively displaced by these different tribes; and the number and strength of its fortified keeps leave us to infer that its annals present the usual record of feuds, assaults, and reprisals. Circles of erect stones, as at Steinster Loch and Bower, and the ruins of Romanist chapels and places of pilgrimage in almost every district, illustrate the changes which have come over its ecclesiastical condition. The most important remains are those of Bucholie Castle, Girnigo Castle, and the tower of Keiss; and on the S.E. coast the castles of Clyth, Swiney, Forss, Latheron, Knockinnan, Berridale, Achastle, and Dunbeath,—of which the last is romantically situated on one of the detached pillars of sandstone rock that are frequent along the Caithness coast. About six miles from Thurso stand the ruins of Braal Castle, the residence of the ancient bishops of Caithness, and on the shores of the Pentland is situated the mythical site of John o’ Groats’ House. The total number of landowners in 1872-3 was 1030,—among the most important being the duke of Portland, with 81,605 acres; Sir John Sinclair of Tollemache, with 78,053; Mrs Thomson Sinclair of Fenswick, with 57,757; Sir Robert Anstruther of Balcaskie in Fife, with 36,597; and the earl of Caithness, with 14,460.

Caithness is divided into ten civil and twelve quoad sacra parishes, and contains twelve churches and two chapels of ease belonging to the Establishment (in four of which there is service in Gaelic); seventeen belonging to the Free Church (in seven of which there is service in Gaelic); one United Presbyterian, and one Roman Catholic at Wick.

The county returns one member to the imperial parliament. The parliamentary constituency in 1875—76 was 1172. The principal towns are Wick and Thurso; the most important villages are Broadhaven, Castletown, Louisburgh, Sarclett, and Staxigoe. The population in 1831 was 34,529; in 1841, 36,343; in 1851, 38,709; and in 1871, 39,992. In the last year the males numbered 18,937, and the females 21,055; and there were in the county at the same date 7474 inhabited houses, 203 vacant, and 431 building.