342 GANGETIC DELTA. Chap. XXXI. 



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.* 



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°, nor sinks below 45°; at this temperature 

 hoar-frost will form on straw, and ice on water placed in 

 porous pans, indicating a powerful radiation. f 



* The natives are familiar with this phenomenon, of which Dr. Baker remem- 

 bers 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. 



+ 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° to 84° ; May and October are the hottest months. The 



