ROSCOM3ION, an inland couuty in the proviuoe of Couuaught, Ireland, is bounded N. -by the oountiea of Sligo and Leitrim ; E. by Leitrim, Longford, and Westmeath ; S. by King's County and Galway ; and W. by Galway and Mayo. It lies between 53' 17' and 54° 8' N. lat. 7° 50' and 8' 47' W. long. Its greatest length from north to .
south is 60 miles, from east to west 40 miles. The area is 949 square miles, or 607,691 acres ; of which 440,522 scree are arable, 130,299 acres uncultivated, 6732 acres in plantations, 768 acres in towns, and 29,370 acres under water. The population in 1831 was 249,618; iu 1811 it was 253,591; in 1851 it was 173,417.
Surface, Ilydregraphy, and county has an irregular outline. Near the centre it suddenly contracts southward to leas than half its greatest breadth, extending in a narrow strip between the rivers Suck and Shannon. Northward the area gradually diminishes till it terminates iu a breadth of three miles. The surface slopes towards the Shannon, and lies within the great plain of Ireland. It consists fur the moat part of bold uodulations. In the southein division a series of elevated ridges, separated by alluvial flats, divide into two ranges, the one skirting the shore of Lough Ree, the other the left bank of the Suck. At a distance of from two to four miles from the Shannon, the surface rise. into the Slieve Bawn range, which reaches at. its southern extremity an elevation of 857 feet. Towards the opposite verge of the couuty the surface is generally level. The only coneiderable elevation iu this district is Slieve Aelwyn, which rises between Castlerea and Ballinlougb to a height of 497 feet. The highest part of the county is iu the north, where the Curlew Hills on the Sligo border near Boyle have an altitude of 863 feet ; and the Braulieve Mountains, 1317 feet high, and Slieve Curkagh, 1098 feet high, extend from Sligo and Leitrim into the district went from Lough Allen.
The principal rivers are the Shannon and the Suck, which form about two-thirds of the whole boundary line of the county. The Shannon, five miles from its source in the county of Leitrim, enters Lough Allen, about the middle of which is the northern limit of Roscommon. From Lough Allen it. flows along the eastern boundary with a winding course and several expansions, forming the chief lakes of Roscommoo, to the southern extremity of the county, where it receives its chief tributary the Suck. The course of the Shannon along the border of Roscommon is about 75 miles in length, with a fall of less than 40 feet, or about six inches to a mile. It Is navigable throughout, except
in a few places where rapids and shoals are passed by canals. [Suet:leo:L] The Arigna and the Boyle are tributaries of the Shannon. The Suck rises within the border of Mayo county, flows eaetward to the town of Castlerea, where it bends to the south, and then runs south-eastward to the western boundary, which it follows, with an interval of about five miles, till it unitee with the Shannon. Its course in all Is about 60 ninon long. It is navigable for fiat-bottomed barges to Ballinaeloe, about 10 miles from the Shannon.
The principal lakes are the several expansions of the Shannon. Lough Allen, the lower half of which borders the county, lies north and south about eight miles long by three or four tulles broad, and about 160 feet above sea-level. Its shores are well-wooded and rise gently towards the fine mountain scenery in the back.-ground. Between Lough Allen and Lough Ree, are Loughs Corry, Tap, Boderig or Bodarg, Sconnell, and Forbes. These are of various sizes, and some of them very irregular In outline. Lough Ree, next to Lough Derg, the largest of all the expansions of the reaches within two miles of the town of Athlone., extending 16 miles from north to south, with aa extreme breadth of 7 nines. The depth of water is from 20 to 30 feet, sinking in some places to 120 feet. The shores nowhere rise higher than 250 feet above the surface of the water, and being shallow and stony are unfavourable for landing. Numerous shoals render the navigation difficult There is not much wood along its banks, and Dot • village is visible from the water, but the lake is 'sodded with Islands, which in many places render the scenery picturesque. Numerous pleasure-boats are kept on the lake. In the north Lough Skean and Meelagh, and in the line of the Boyle River Lough Gars, which is five miles in length and breadth, Lough Key or Rockingham Lough, and Lough Oakport, all communicate with the Shannon, and are remarkable for their beautiful and picturesque scenery. There are • number of smaller lakes in the county. In many parts of the limestone tracts are temporary lakes, called turloughs, which are filled with water in winter, but are usually dry in summer, being drained off by fissure' in the rock as the vegetable matter that stopped them decays with the progress of the season. They yield excellent crops where the bottom is greasy, and early enough left dry.