SHANNON, a river of Ireland, one of tho largest in the kingdom, has a course of 220 unites, and affords a navigable line of communi cation, which nearly intersects Ireland from north to south. It rises about 20 miles east from Sligo, and expanding at intervals into lakes, falls into the sea between the Loop and Kerry heads, 56 miles below Limerick. The Shannon is the outlet for the waters of an immense tract of country, and it gives facilities for commercial intercourse, not only by its communication with the sea, but also with the metro polis by means of two canals. This river must be viewed under two distinct beads, as it is locally known under two distinct names, namely —the Lower Shannon, including that portion of the river below Lime rick, which is connected with the external commerce of the country; and the Upper Shannon, from its source down to Limerick, which is connected with its Internal commerce.
The source of this noble stream is generally considered to be a circular basin of about 20 feet in diameter, situated at the southern base of the Cuilcagh Mountain, in Cavan county, whence it flows in a deep dead sluggish stream into Lough Allen, in the county of Leitrim County of], a small basin about 8 miles long and 3 to 4 miles broad, lying in the midst of a coal district, and 115 feet below the level of the source. Other small streams fall into this lake, almost any one of which may bo considered the parent of this great river. Of these the largest are the Owenmore nod the Dorbally, which join tho Shannou before falling into the lake.
Leaving Lough Allen, tho river is so obstructed by shallows, that a canal, passing to the eastward of it was cut, and since improved by the Shannon Commissioners, from its southern extremity near Drum ahambo, to Battle-Bridge, a distance of nearly 5 miles ; on this, as on most of the canals cut for the Shannon navigation, the fall is over come by locks. From this point the river runs in a southerly direction, with a mid-channel depth varying from 5 to 20 feet, for 6 miles, when it receives the Boyle River from Lough Gars and Lough Key. By the removal of shoals, and the construction of a regulating weir and a lock at Knockvicar, near the entrance to Lough Key, the river has been rendered navigable to within a mile of the town of Boyle. A mile below this point atanibi the town of Carrick-on-Shannon, where a quay-wall and harbour have been formed, and two miles farther occurs a small cap/nion called Corry Lough, whence the course of the river is tolerably straight and good as far as Jamestown, a of two miles. Hero a weir has been formed, and a shallow circuitous bend is avoided by a canal two miles in length. Ou this canal there Is a lock 110 feet long and 30 feet broad. From a mile below this innsl nearly down to Ituskey are a series of small lakes surrounded by low hills, with diversified and in some parte well-wooded scenery. At Ituskey there is a regulating weir and lock. Two miles and a half below Ruakey the Shannon caters Lough Forbes [Loaurono], which has an average depth of 7 or S feet, and has been cleared of its only obatruotion, a shoal of small extent near the ceutro, where the lake is contracted to a breadth of only 350 yards. The removal of other shoal., and the construction of a weir and lock at Tarmonbarry, where a commodious wharf has also been formed, complete the upper navigation as far as Richmond Harbour, the grand depOt of the Royal Canal Company, near the village of Cloondrah. Between this and banesborongh, a distance of seven miles, the river is of an average breadth of 250 yards. At Lauesborough the Shannon is crossed by a atone bridge, with a awing-bridge for the passage of vessels. Above and below the bridge the river has been deepened, and by an improved channel the navigation here enters Lough Ree. [Itoscomaroar, County of.] Lough flee is the second expansion of the Shannon in point of magni tude, as it is in order, from the mouth ; it extends 16 miles in a north and south direction, and reaches within two miles of Athlone. From Lough Itee to Athlone, where the river was formerly much obstructed by eel-weirs and shallows, great improvements have been mades the, channel has been deepened, and a regulating weir constructed, with a lock 170 feet long by 40 feet wide. There is also a spacious lauding wharf, and a ucw bridge has been erected, with a swivel bridge over the line of navigation. Between this place and Lough Derg the river makes two largo bends, and dividing itself into various branches forms islands, some of which are of considerable size. At Shannon Bridge, a military station 134 miles below Athlone, the river has been deepened,- the bridge underpinned and opened by a swivel-bridge, and an extensive landing wharf has been formed. A little lower the Suck
enters the Shannon. lu consequence of the recent improvements the waters of the Shannon have here been so much kept within their proper channel, as to relieve nearly 19,000 acres from flooding. The Suck, which forms the division between the counties of Galway and Roscommon, is a very fine river, and appears at its junction scarcely inferior to the Shannon itself, of which it is the largest tributary. It rises near Castlereagh, in the county of Roscommon, and has a circuitous course of about 60 miles, receiving in its passage a number of tributary streams. The Shannon receives at Shannon Harbour the Brescia from Kiug's County, and the Grand Canal from Dublin. Immediately opposite is a branch of the cans!, which runs up to 13allinasloe. About five miles lower, above the falls of 3leelick and Killoguea, which are the greatest in the whole lice above Killaloe, weir, with a lock 170 feet long by 40 feet wide, and having a fall of 8 feet, has been erected. From below the falls, where it is joined by the Lower Brosna, the river affords a wide channel, generally above 20 feet deep, and marked out by beacons, to the entrance of Lough Derg, a distance of nine miles. The shores between Loughs flee and Derg are low, consisting of lands of a rich calcareous nature, producing large crops of rank coarse grata, and affording pasturage for cattle. These rich lands are generally backed by bog-land elevated from 20 to 30 feet above the river, and towards Athlone by low rounded isolated limestone hills. There are few places where good firm land comes down to the river's edge. About a mile below Portman, the river enters Lough Derg, which is 20 miles iu length, and varies in breadth from three-quarters of a mile to three miles direct distance, with large bays on both sides, which in some places cause an expanse of seven or eight miles. The scenery of this lake is very beautiful, especially towards the southern extremity, where it lies between hills of considerable elevation terminating abruptly on the lake. All the north-western shore, which forma part of the county of Galway, is low and abounds in bog-laud. The Tipperary shore, which forms all the eastern side of the Like, is greatly diversified in appearance and character ; to the north it consists of rounded lime stone-hills, which are chiefly used for pasture, while to the south the mountains are higher, more abrupt, and consist of slate formation, which is worked to great advantage. The opposite shore, part of the county of Clare, is of like formation. Lough Derg contains few islands, but it abounds in rocks and dangerous shoals, and the shores, like those of Lough flee, are difficult of approach from being so shallow and stony. The greatest depth is 120 feet; the southern portion is generally much deeper than that to the northward. The bottom is of marl, which is dredged up iu great quantities for manure. At Mount Shannon, on the western shore of the lough, a pier and wharf have been constructed for the accommodation of the steamers plying on the river. At Killaloe, about a mile below Lough Derg, the channel has been deepened, and a regulating weir, 1160 feet long, has been raised across tho river. From this place to Tarmonbarry, at the entrance of the Royal Canal, a distance of 85 miles, steamers of 200-horse power are daily plying, and the lakes aro traversed by tug steamers, towing trade-barges of from GO to•100 tons burden. At i Killaloe is the chief depot and dockyard of the inland department of the Dublin Steam Navigation Company. • The Limerick navigation, which includes that part of the river I between Killaloo and the city of Limerick, has a fall of 97 feet, which is overcome by a canal at each end and two regulating weirs. A series of falls below Killaloe-bridge is passed by is canal two miles long, cut close by the river on the Clare side. The rapids at O'Bricu'e bridge and at Thirteen have been deepened, a weir and lock have been constructed at Corbally and World's End, a tracking bridge has been erected over the river at Plessey, and by the removal of numerous shoals the bed of the river has been rendered available to the utmost for the navigation of trade-barges. The communication• with the Lower Shannon and the harbour of Limerick is completed by a n mile long. Immediately above Limerick the river divides into tw/ branches, forming King's Island, on which the old town stands, wPd the cathedral, castle, and other public buildings. Just above 1)10 reunion of these two branches is the last fall of the river.