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.]