Successive depressions of

the delta.

Its subter

ranean structure.

Care has been taken not to overstate the work performed by the Bengal rivers. Borings have been carried down to 481 feet at Calcutta, but the auger broke at that depth, and it is impossible to say how much farther the alluvial deposits may go. There seem to have been successive eras of vegetation, followed by repeated depressions of the surface. These successive eras of vegetation now form layers of stumps of trees, peat-beds, and carbonized wood. Passing below traces of recently submerged forests, a well- marked peat - bed is found in excavations around Calcutta at a depth varying from 20 to 30 feet; and decayed wood, with pieces of fine coal, such as occur in mountain streams, has been met with at a depth of 392 feet. Fossilized remains of animal life have been brought up from 372 feet below the present surface. The footnote 1 illustrates the successive layers of the vast and lofty island, so to speak, which the rivers have built up-an island with an area of 50,000 square miles, and 400 feet high from its foundation, although at places only a few inches above sea-level.

1 Abstract Report of Proceedings of Committee appointed to superintend the Borings at Fort-William, December 1835 to April 1840.' 'After penetrating through the surface soil to a depth of about 10 feet, a stratum of stiff blue clay, 15 feet in thickness, was met with. Underlying this was a light-coloured sandy clay, which became gradually darker in colour from the admixture of vegetable matter, till it passed into a bed of peat, at a distance of about 30 feet from the surface. Beds of clay and variegated sand, intermixed with kankar, mica, and small pebbles, alternated to a depth of 120 feet, when the sand became loose and almost semi-fluid in its texture. At 152 feet, the quicksand became darker in colour and coarser in grain, intermixed with red water-worn nodules of hydrated oxide of iron, resembling to a certain extent the laterite of South India. At 159 feet, a stiff clay with yellow veins occurred, altering at 163 feet remarkably in colour and substance, and becoming dark, friable, and apparently containing much vegetable and ferruginous matter. A fine sand succeeded at 170 feet, and this gradually became coarser, and mixed with fragments of quartz and felspar, to a depth of 180 feet. At 196 feet, clay impregnated with iron was passed through; and at 221 feet sand recurred, containing fragments of limestone with nodules of kankar and pieces of quartz and felspar; the same stratum continued to 340 feet; and at 350 feet a fossil bone, conjectured to be the humerus of a dog, was extracted. At 360 feet, a piece of supposed tortoiseshell was found, and subsequently several pieces of the same substance were obtained. At 372 feet, another fossil bone was discovered, but it could not be identified, from its being torn and broken by the borer. At 392 feet, a few pieces of fine coal, such as are found in the beds of mountain streams, with some fragments of decayed wood, were picked out of the sand, and at 400 feet a piece of limestone was brought up. From 400 to 481 feet, fine sand, like that of the seashore, intermixed largely with shingle composed of fragments of primary rocks, quartz, felzpar, mica, slate, and limestone, prevailed, and in this stratum the bore has been terminated.'

SILT BROUGHT DOWN BY GANGES.

27

silt.

It should be remembered, however, that the rivers have Upper Bengal been aided in their work by the sand deposited by the finished' ocean currents. But, on the other hand, the alluvial deposits by river of the Ganges and Brahmaputra commence far to the north of the present delta-head, and have a total area greatly exceeding the 50,000 square miles mentioned in a former paragraph. The Brahmaputra has covered with thick alluvium the valley of Assam; its confluent, the Meghná, or rather the upper waters which ultimately form the Meghná, have done the same fertilizing task for the valleys of Cachar and Sylhet ; while the Ganges, with its mighty feeders, has prepared for the uses of man thousands of square miles of land in the broad hollow between the Himálayas and the Vindhyas, far to the north-west of its present delta. A large quantity of the finest and lightest silt, moreover, is carried out to sea, and discolours the Bay of Bengal 150 miles from the shore. The plains of Bengal are truly the gift of the great rivers.

of silt

Several attempts have been made to estimate the time which Amount the Ganges and Brahmaputra must have required for ac- brought complishing their gigantic task. The borings already cited, down. together with an admirable account by Colonel Baird Smith in the Calcutta Journal of Natural History,1 and the Rev. Mr. Everest's calculations, form the chief materials for such an estimate. Sir Charles Lyell 2 accepts Mr. Everest's calculation, made half a century ago, that the Ganges discharges 6368 millions of cubic feet of silt per annum at Gházípur.

This would alone suffice to supply 355 millions of tons a year, Ganges or nearly the weight of 60 replicas of the Great Pyramid. It is silt at Ghazipur. scarcely possible,' he says, 'to present any picture to the mind which will convey an adequate conception of the mighty scale of this operation, so tranquilly and almost insensibly carried on by the Ganges.' About 96 per cent. of the whole deposits are brought down during the four months of the rainy season, or as much as could be carried by 240,000 ships, each of 1400 tons burthen. The work thus done in that season may be realized if we suppose that a daily succession of fleets, each of two thousand great ships, sailed down the river during the four months, and that each ship of the daily 2000 vessels deposited a freight of 1400 tons of mud every morning into the estuary.

1 Vol. i. p. 324. The other authorities, chiefly from the Journal of the Bengal Asiatic Society, are fully quoted in the Geology of India, by Messrs. Medlicott and Blanford, vol. i. pp. 396 et seq. (Calcutta Government Press, 1879).

* Principles of Geology, vol. i. pp. 478 ct seq. (1875).

Estimated

silt of

united river

system at the delta.

Time required by rivers to

construct

the delta.

River

But the Ganges at Gházípur is only a single feeder of the mighty mass of waters which have formed the delta of Bengal. The Ganges, after leaving Ghazipur, receives many of its principal tributaries, such as the GOGRA, the SON, the GANDAK, and the KUSI. It then unites with the Brahmaputra, and finally with the Meghná, and the total mass of mud brought down by these combined river systems is estimated by Sir Charles Lyell to be at least six or seven times as much as that discharged by the Ganges alone at Gházipur. We have therefore, at the lowest estimate, about 40,000 millions of cubic feet of solid matter spread over the delta, or deposited at the river mouths, or carried out to sea, each year; according to Sir Charles Lyell, five times as much as is conveyed by the Mississippi to its delta and the Gulf of Mexico. The silt borne along during the rainy season alone represents the work which a daily succession of fleets, each of 13,000 ships a-piece, sailing down the Ganges during the four rainy months would perform, if each ship of the daily 13,000 vessels discharged a freight of 1400 tons a-piece each morning into the Bay of Bengal. This vast accumulation of silt takes place every rainy season in the delta or around the mouths of the Ganges; and the process, modified by volcanic upheavals and depressions of the delta, has been going on during uncounted thousands of years.

General Strachey took the area of the delta and coast-line within influence of the deposits at 65,000 square miles, and estimated that the rivers would require 45'3 years to raise it by I foot, even by their enormous deposit of 40,000 millions of cubic feet of solid earth per annum. The rivers must have been at work 13,600 years in building up the delta 300 feet. But borings have brought up fluvial deposits from a depth of at least 400 feet. The present delta forms, moreover, but a very small part of the vast alluvial area which the rivers have constructed in the great dip between the Himálayas and the Vindhyan mountains. The more closely we scrutinize the various elements in such estimates, the more vividly do we realize ourselves in the presence of an almost immeasurable labour carried on during an almost immeasurable past.

The land which the great Indian rivers thus create, they also irrigation. fertilize. In the lower parts of their course we have seen how their overflow affords a natural system of irrigation and manuring. In the higher parts, man has to step in, and to bring their water by canals to his fields. Some idea of the enormous irrigation enterprises of Northern India may be obtained in the four articles in The Imperial Gazetteer on the

GANGES AND JUMNA CANALS.

29

Ganges and Jumna canals. The Ganges Canal had, in 1883, a length of 445 miles, with 3428 miles of distributaries; an irrigated area of 856,035 acres (including both autumn and spring crops); and a revenue of £279,449, on a total outlay of 2 millions sterling (£2,767,538 to 1883). The Lower Ganges Canal will bring under irrigation nearly 1 million acres (including both autumn and spring crops). It has already (1882-83) a main channel of 556 miles, with 1991 miles of distributaries; an irrigated area of 606,017 acres; and a clear revenue of £107,000, or 4'13 per cent. on the total outlay up to 1883 (£2,589,624). The Eastern Jumna Canal has a length of 130 miles, with 618 miles of main distributaries. In 1883, the total distributaries aggregated nearly 900 miles, with an irrigated area of 240,233 acres; and a revenue of £82,665, or 284 per cent. on the total outlay to that year (£290,839). The Western Jumna Canal measures 433 miles, with an aggregate of 259 miles of distributing channels, besides private watercourses, irrigating an area of 374,243 acres ; with a revenue of £74,606, or 8'4 per cent. on a capital outlay to 1883 of £884,952. The four Ganges and Jumna Canals, therefore, already irrigate an aggregate area of over two million acres, and will eventually irrigate over three millions. Among many other irrigation enterprises in Upper India are the Agra, Bári Doáb, Rohilkhand and Bijnor, Betwá, and the Sutlej-Chenab and Indus Inundation Canals.

ways.

The Indian rivers form, moreover, as we have seen, the great The Rivers highways of the country. They supply cheap transit for the as highcollection, distribution, and export of the agricultural staples. What the arteries are to the living body, the rivers are to the plains of Bengal. But the very potency of their energy some- The Rivers times causes terrible calamities. Scarcely a year passes without as defloods, which sweep off cattle and grain stores and the thatched cottages, with anxious families perched on their roofs.

In their upper courses, where their water is carried by canals to the fields, the rich irrigated lands breed fever, and are in places rendered sterile by a saline crust called reh. Farther down, the uncontrollable rivers wriggle across the face of the country, deserting their old beds, and searching out new channels for themselves, sometimes at a distance of many miles. Their old banks, clothed with trees and dotted along their route with villages, run like high ridges through the level rice-fields, and mark the deserted course of the river.

It has been shown how the Brahmaputra deserted its main channel of the last century, and now rushes to the sea by a

stroyers.

Changes of river. beds.

Deserted rivercapitals.

The bore

new course, far to the westwards. Such changes are on so vast a scale, and the eroding power of the current is so irresistible, that it is perilous to build large or permanent structures on the margin. The ancient sacred stream of the Ganges is now a dead river, which ran through the Districts of Húglí and the 24 Parganás. Its course is marked by a line of tanks and muddy pools, with temples, shrines, and burning gháts along high banks overlooking its deserted bed.

Many decayed or ruined cities attest the alterations in riverbeds within historic times. In our own days, the Ganges passed close under Rájmahal, and that town, once the Muhammadan capital of Bengal, was (1850-55) selected as the spot where the railway should tap the river system. The Ganges has now turned away in a different direction, and left the town high and dry, 7 miles from the bank. In 1787-88, the TISTA, a great river of Northern Bengal, broke away from its ancient bed. The ATRAI, or the old channel, by which the Tístá waters found their way into the Ganges, has dwindled into a petty stream, which, in the dry weather, just suffices for boats of 2 tons burthen; while the Tístá has branched to the eastwards, and now pours into the Brahmaputra. In 1870, the RAVI, one of the Five Rivers of the Punjab, carried away the famous shrine of the Sikhs near DERA NANAK, and still threatens the town.

If we go back to a more remote period, we find that the whole ancient geography of India is obscured by changes in the courses of the rivers. Thus, Hastinapur, the Gangetic capital of the Pandavas, in the Mahábhárata, is with difficulty identified in a dried-up bed of the Ganges, 57 miles northeast of the present Delhi. The once splendid capital of KANAUJ, which also lay upon the Ganges, now moulders in desolation 4 miles away from the modern river-bank. The remnant of its inhabitants live for the most part in huts built up against the ancient walls.

A similar fate on a small scale has befallen Kushtiá, the river terminus of the Eastern Bengal Railway. The channel silted up (1860-70), and the terminus had to be removed to Goálanda, farther down the river. On the HUGLI river1 a succession of emporia and river-capitals have been ruined from the same cause, and engineering efforts are required to secure the permanence of CALCUTTA as a great port.

An idea of the forces at work may be derived from a single well-known phenomenon of the Húglí and the Meghná, the bore. The tide advances up their broad estuaries until checked 1 See article HUGLI RIVER, The Imperial Gazetteer of India.