IRAWADI, the principal river of Burma and Pegu, rises in the S. slopes of the Patkoi moun tains,—one branch in lat. 27° 43' N., long. 25' E., and another in the same hills a few days' journey farther eastward. These two, known as the Myit-gyi or large river, and the Myit-nge or small river, respectively, unite to form the Irawadi in about lat. 26° N. The springs aro reported to be fed by large snow beds and a few glaciers. In March the river begins to rise, and gradually increases its volume till its waters are forty feet above their lowest level. They rapidly subside in October, when the rains cease and the N.E. mon soon begins.
It runs nearly N: to S. through Burma and Pegu, and discharges itself by nine different mouths into the Bay of Bengal, after a course of 1060 miles. It receives the Khyendwcn, 470 miles ; Shwely, 180 miles ; and the Moo, 125 miles ; and it drains 164,000 square miles. The chief tributaries of the Irawadi, in British terri tory, are the Ma-htun (or Meng-dun), the Ma-de, and Thai-lai-dan from the W. ; and the Kyeni, Bhwotlay, and Na-weng from the E. Its tide is felt as far up as Henzada, and at Puzwondoung it rises 181 feet at springs. The Bassein branch affords a passage for the largest ships for 60 miles from its mouth. No river of similar magni tude presents so few obstructions to navigation. Amongst the high mountains at its source the rainfall is considerable ; at its centre, the fall of rain is comparatively small, but much rain falls at its delta. From the entrance of the Nam Yang downwards, the valley of the Nam Keng is generally very flat, and of some considerable width, and numerous marshy tracts appear on either side of the river. The average length of the Nam Kang, from the mouth of the Nam Yang down to its junction with the Irawadi at Katikyo Nainmo, including the numerous curves, amounts to 52 miles. From the entrance of the Nam Keng to Amarapura, the river has a real length of 269 miles •, from Amarapura to the head of the delta at Sakkemun, 370 miles. The delta forms a triangle, nearly equilateral, with sides of 160 miles, the enclosed area consequently amounting to 9742 square miles. Towards Pegu and Sitan the Irawadi widens considerably, in of the accession of the Pan-lan river, and its limits become less sharply defined. The valley of Hukum is stated to be 1000 feet above the level of the sea. The central branch of the Irawadi, at Manchi, in lat. 27° 20' N., where it was visited by Wilcox, has an elevation of 1800 feet, and runs over a pebbly bed. Its elevation at Bhamo, in lat. 24°, is estimated by the same authority to be about 500 feet. The valley of Manipur is drained by the most westerly tributary of the Irawadi, and it is separated from Cachar by a mountain range, which is 6000 or 8000 feet' high, is pine-clad towards the summit. The valley of Hukum or Hookoom was visited by Griffith ; it is more open, but is sur rounded on the N. and E. by mountains elevated 5000 and 6000 feet, and is traversed by numerous ranges of low hills. Griffith's own account of the Irawadi above Bhamo is,- that it keeps up its magnificent. character, as far as he went, to the mouth of the Mogoung river, where it is 900 to 1000 yards across, and he describes the appearance of its vast sheet of water as really grand. At
the beginning of the first defile, about five miles above Bhamo, the river is about 1000 yards across, and its course is defined by low-wooded hills which run close to its banks. About two miles farther on, the channel narrows to 500 yards, and the hills become even closer and hang more 'abruptly over the stream than before, and about another mile beyond, a higher range of hills from the S.W. comes in behind the former one, and both terminate on the bank as two headlands. Upon the right •bank of • the. Irawadi, the moun tains opposite Than Yun Yova, hi lat. 24° 361' N., long. 96° 311' E., have an average height of from 6000 to 7000 feet. One of the highest, the sum mit of which is visible from the valley, reaches apparently 8000 feet. Westward of 'Let-pan Zin Yova, at a little distance from the right bank, lat. 24° 27' 2" N., long. 95° 56' 15" E. the summits of the mountains attain a height Of 2000 feet. Heights of 800 and even 1000 feet are also numerous on the right bank of the river, only 20 to 23 miles N. of Shue-mut-thophya, lat. 23° 4' N., long. 96° 15' E.
The character of the whole river district, including the elevations not above from 3000 to 4000 feet, presents a thoroughly tropical appear-1 ance. The declivities of the hills, as well as the valley of the river are covered with the wildest and most diversified vegetation, in the shape of dense tree and grass jungles.
The bore in this river is occasionally but in the neighbouring Sitang river its fury is great, and occasions much loss of life. Burmans name thirty feet as the height to which it occa sionally rises, and this may perhaps be the case in the bends of the river, where the rush has attained its full speed, before being deflected to the next bend. Even in the Hoogly, near the bend at Chandpal Ghat, the pointed curling wave may be seen several feet high. In the Irawadi and Mekong basins, there are remnants of tribes strongly dis tinguished from the predominant races, and tend ing, with the evidence of language, to show that the ethnic history of Ultra-India is very ancient, and has undergone repeated revolutions.
Its delta extends for 130 miles from Porian point to Rangoon river. Through its delta run nine principal branches, the names of which are, the Bassein or Negrais, the Thek-ngay-thoung, the Kyun-tun, the Peah-ma-lau, the Irawadi, the Dallah, the Pyapun, the China Buckeer or Tdoo, and the Rangoon rivers. Their mouths are fronted by extensive shoals, formed from the detritus brought down by the rivers. The amount of water which the Irawadi pours into the sea is about two-thirds that of the Ganges.
In the delta there is a maritime vegetation of mangroves, Sonneratia, Heritiera, Exccecaria, and other saline plants, just as in similar salt-marshes along the coast of the tropics. Irawadi is derived from Airavati, the elephant of Indra.—Schlagent ' weit, General Hypsometry of India, ii. p. 101 ; Oldham in Yule's Embassy; Hooker and Thomson's Flora Indica.