Tho great alluvial low-level tract of Northern India, watered by the Ganges and Indus and their tributaries, is known as the lndo-Gangetic plain. It is an immense expanse of flat country stretching from sea to sea, entirely composed of alluvial de posits of very late geological age, and separating the hilly ground of the Peninsula from the various mountain and hill ranges of Sind, the Panjab, the Himalaya, Assam, Burma. The geological forma tions of the peninsular area are arranged in the Manual of Geology as recent and post-tertiary, emnozoic, mesozoic, palmozoic, and azoic, the last comprising the Vindhyan series, the transition, and the metamorphic or gneissic. The formations in extra-peninsular territories being recent and post-tertiary, pliocene, miocene, eocene, cretaceous, jurassic, trial, permian, carboniferous, and silurian and infra-silurian, all the infra-silurian being non -fossiliferous.
Rivers.—The navigable rivers of India are the Ganges, the Indus, the Brahmaputra, the Irawadi. The Ganges rises in the Garhwal State, in lat. 30° 56' N., and 79° 6' 40" E., and enters the Bay of Bengal by many mouths, after a course of 1557 miles. Under the name of Bhagirathi, it issues from an ice-cave at the foot of a Himalayan snow-bed, 13,800 feet above the sea. Twelve rivers of British India are deemed holy by the Hindus, and the pushkaram festival is held at them. But the Ganges is the most sacred. To live on its banks, or near it, is a happiness; and to die on its banks, or in its waters, a great privi lege. It is used for navigation and for irrigation. Its catchment basin is 39.1,100 square miles, and maximum flood-discharge 1,800,000 cubic feet per second.
The Jumna, Jamna, or Yamuna, joins the Ganges at Allahabad, after a course of 680 miles. Its source is in Garhwal, in the Himalaya, 5 miles N. of Jumnotri, 10,849 feet above the sea ; and its catchment basin is 118,000 square miles. On its banks are the cities of Hamirpur, Agra, and Dehli; the eastern and western Jumna canals have been led from it at Faizabad and above Agra, but in the hot weather it dwindles to a small stream. The Jumna at Agra, and at other places, since many years had been bridged by a line of boats, and now splendid railway bridges span it at Dehli, Agra, and Allahabad.
The Brahmaputra river course is 1800 miles; and it is navigable for steamers up to Dibrugarh, 800 miles from the -sea. Its drainage basin is 361,200 square miles. Its valley is the province of Assam, and many tribes occupy both its banks. At
Goalanda, about half-way between the . delta head and the sea, the Ganges unites with the main stream of the Brahmaputra, and farther down with the Megua. Their combined waters represent the drainage collected by the two vast river-systems from an aggregate catchment basin of 752,000 square miles on both sides of the Hima laya, together with the rainfall poured into the Megna from the Burmese watershed.
The Indus river was known to the Greeks as the Sindhu or 1/14,4. It rises in lat. 32° N., and long. 81° E., on the north-western slope of the Kailas mountain,.the Sutlej river rising on its southern slope, and the Brahmaputra, under its Tibetan name of Tsang-pu, at some distance from its eastern base, in lat. 31° N., and long. 83° E., and 16,000 feet above the sea, the Dihang river being supposed the connecting link between the Tsang pu of Tibet and the Brahmaputra of Assam. The Indus pours its waters into the Arabian Sea after a course of 1800 miles, its drainage ba'sin being 372,700 square miles.
The Ravi in the Panjab is the Hydraotes of Arrian, the Sanskrit Airavati. This stream has been utilized to supply the Bari Doab canal. In March and April its depth on the borders of the district of Amritsar is not more than a foot, Between June and September it rises to 18 or 20 feet. The main bed alters but little, and the greatest volume of water only floods a mere fringe on either bank. In 1870 it carried away a Sikh shrine near Dera Nanuk, and it still threatens damage.
The Irawadi river (Airavati), after a course of 900 miles, disembogues by several mouths into the Gulf of Martaban. It rises, by two branches, from the Patkoi mountains, one of them in lat. 27° 43' N., and long. 97° 25' E., the other a little to the east, the Myit-gyee and Myit-gne, which unite about lat. 26° N., and run to the south along a catchment basin of 158,000 square miles. It is navigable above 500 miles north to Bhamo ; and at Mogoung, when at its lowest, the bottom was not sounded at 40 fathoms.
The Koladyn or Kuladan, a river of Arakan, is supposed to have its origin near the Blue Moun tain (22° 37' N.), and it passes the town of Akyab to enter the Bay of Bengal. It is navigable for 50 miles for vessels of 300 or 400 tons.
The chief rivers of the Peninsula of India, are the Mahanadi, Godavery, Kistna, and Cauvery, and, though not navigable, are valuable for irrigation.