On the 14th we passed the Dacca river; below which the Megna is several miles wide, and there is an appearance of tide, from masses of purple Salvinia (a floating plant, allied to ferns), being thrown up on the beach like sea-weed. Still lower down, the vegetation of the Sunderbunds commences; there is a narrow beach, and behind it a mud bank several feet high, supporting a luxuriant green jungle of palms (Borassus and Phoenix), immense fig-trees, covered with Calami, and tall betel-palms, clothed with the most elegant drapery of Arostichum scandens, a climbing fern with pendulous fronds.
Towards the embouchure, the banks rise ten feet high, the river expands into a muddy sea, and a long swell rolls in, to the disquiet of our fresh-water boatmen. Low islands of sand and mud stretch along the horizon: which, together with the ships, distorted by extraordinary refraction, flicker as if seen through smoke. Mud is the all prevalent feature; and though the water is not salt, we do not observe in these broad deltas that amount of animal life (birds, fish, alligators, and porpoises), that teems in the narrow creeks of the western Sunderbunds.
We landed in a canal-like creek at Tuktacolly,* ["Colly" signifies a muddy creek, such as intersect the delta.] on the 17th, and walked to Noacolly, over a flat of hard mud or dried silt, covered with turf of Cynodon Dactylon. We were hospitably received by Dr. Baker, a gentleman who has resided here for twenty-three years; and who communicated to us much interesting information respecting the features of the Gangetic delta.
Noacolly is a station for collecting the revenue and preventing the manufacture of salt, which, with opium, are the only monopolies now in the hands of the East India Company. The salt itself is imported from Arracan, Ceylon, and even Europe, and is stored in great wooden buildings here and elsewhere. The ground being impregnated with salt, the illicit manufacture by evaporation is not easily checked; but whereas the average number of cases brought to justice used to be twenty and thirty in a week, they are now reduced to two or three. It is remarkable, that though the soil yields such an abundance of this mineral, the water of the Megna at Noacolly is only brackish, and it is therefore to repeated inundations and surface evaporations that the salt is due. Fresh water is found at a very few feet depth everywhere, but it is not good.
When it is considered how comparatively narrow the sea-board of the delta is, the amount of difference in the physical features of the several parts, will appear most extraordinary. I have stated that the difference between the northern and southern halves of the delta is so great, that, were all depressed and their contents fossilised, the geologist who examined each by itself, would hardly recognise the two parts as belonging to one epoch; and the difference between the east and west halves of the lower delta is equally remarkable.
The total breadth of the delta is 260 miles, from Chittagong to the mouth of the Hoogly, divided longitudinally by the Megna: all to the west of that river presents a luxuriant vegetation, while to the east is a bare muddy expanse, with no trees or shrubs but what are planted On the west coast the tides rise twelve or thirteen feet, on the east, from forty to eighty. On the west, the water is salt enough for mangroves to grow for fifty miles up the Hoogly; on the east, the sea coast is too fresh for that plant for ten miles south of Chittagong. On the west, fifty inches is the Cuttack fall of rain; on the east, 90 to 120 at Noacolly and Chittagong, and 200 at Arracan. The east coast is annually visited by earthquakes, which are rare on the west; and lastly, the majority of the great trees and shrubs carried down from the Cuttack and Orissa forests, and deposited on the west coast of the delta, are not only different in species, but in natural order, from those that the Fenny and Chittagong rivers bring down from the jungles.* [The Cuttack forests are composed of teak, Sal, Sissoo, ebony, Pentaptera, Buchanania, and other trees of a dry soil, and that require a dry season alternating with a wet one. These are unknown in the Chittagong forests, which have Jarool (Lagerstroemia) Mesua, Dipterocarpi, nutmegs, oaks of several kinds, and many other trees not known in the Cuttack forests, and all typical of a perennially humid atmosphere.]
We were glad to find at Noacolly that our observations on the progression westwards of the Burrampooter (see chapter xxvii) were confirmed by the fact that the Megna also is gradually moving in that direction, leaving much dry land on the Noacolly side, and forming islands opposite that coast; whilst it encroaches on the Sunderbunds, and is cutting away the islands in that direction. This advance of the fresh waters amongst the Sunderbunds is destructive to the vegetation of the latter, which requires salt; and if the Megna continues its slow course westwards, the obliteration of thousands of square miles of a very peculiar flora, and the extinction of many species of plants and animals that exist nowhere else, may ensue. In ordinary cases these plants, etc., would take up their abode on the east coast, as they were driven from the west; but such might not be the case in this delta; for the sweeping tides of the east coast prevent any such vegetation establishing itself there, and the mud which the eastern rivers carry down, becomes a caking dry soil, unsuited to the germination of seeds.
On our arrival at Calcutta in the following February, Dr. Falconer showed us specimens of very modern peat, dug out of the banks of the Hoogly a few feet below the surface of the soil, in which were seeds of the Euryale ferox:* [This peat Dr. Falconer also found to contain bones of birds and fish, seeds of Cucumis Madraspatana and another Cucurbitaceous plant, leaves of Saccharum Sara and Ficus cordifolia. Specks of some glistening substance were scattered through the mass, apparently incipient carbonisation of the peat.] this plant is not now known to be found nearer than Dacca (sixty miles north-east, see chapter xxvii), and indicates a very different state of the surface at Calcutta at the date of its deposition than that which exists now, and also shows that the estuary was then much fresher.
The main land of Noacolly is gradually extending seawards, and has advanced four miles within twenty-three years: this seems sufficiently accounted for by the recession of the Megna. The elevation of the surface of the land is caused by the overwhelming tides and south-west hurricanes in May and October: these extend thirty miles north and south of Chittagong, and carry the waters of the Megna and Fenny back over the land, in a series of tremendous waves, that cover islands of many hundred acres, and roll three miles on to the main land. On these occasions, the average earthy deposit of silt, separated by micaceous sand, is an eighth of an inch for every tide; but in October, 1848, these tides covered Sundeep island, deposited six inches on its level surface, and filled ditches several feet deep. These deposits become baked by a tropical sun, and resist to a considerable degree denudation by rain. Whether any further rise is caused by elevation from below is doubtful; there is no direct evidence of it, though slight earthquakes annually occur; and even when they have not been felt, the water of tanks has been seen to oscillate for three-quarters of an hour without intermission, from no discernible cause.* [The natives are familiar with this phenomenon, of which Dr. Baker remembers two instances, one in the cold season of 1834-5, the other in that of 1830-1. The earthquakes do not affect any particular month, nor are they accompanied by any meteorological phenomena.]
Noacolly is considered a healthy spot, which is not the case with the Sunderbund stations west of the Megna. The climate is uniformly hot, but the thermometer never rises above 90 degrees, nor sinks below 45 degrees; at this temperature hoar-frost will form on straw, and ice on water placed in porous pans, indicating a powerful radiation.* [The winds are north-west and north in the cold season (from November to March), drawing round to west in the afternoons. North-west winds and heavy hailstorms are frequent from March to May, when violent gales set in from the southward. The rains commence in June, with easterly and southerly winds, and the temperature from 82 degrees to 84 degrees; May and October are the hottest months. The rains cease in the end of October (on the 8th of November in 1849, and 12th of November in 1850, the latest epoch ever remembered): there is no land or sea breeze along any part of the coast. During our stay we found the mean temperature for twelve observations to be precisely that of Calcutta, but the humidity was more, and the pressure 0.040 1ower.] We left Noacolly on the 19th for Chittagong; the state of the tide obliging us to go on board in the night. The distance is only 100 miles, but the passage is considered dangerous at this time (during the spring-tides) and we were therefore provided with a large vessel and an experienced crew. The great object in this navigation is to keep afloat and to make progress towards the top of the tide and during its flood, and to ground during the ebb in creeks where the bore (tidal wave) is not violent; for where the channels are broad and open, the height and force of this wave rolls the largest coasting craft over and swamps them.