PA11T 1.] 
Alluvial deposits of the Irawadi, Sfc. 
25 
It may perhaps seem strange, that, with so eminently level and low lying a tract of 
country as I have described above, over which flood waters are repeatedly effused, no consi¬ 
derable deposit of river sediment has taken place. The objection is to some extent plausible, 
but I shall now hazard a few considerations which greatly diminish its force. In the first 
place I would beg attention to the fact previously stated by me, which lies at the root of the 
entire question, and that is, that the Irawadi delta is at this present time in the precise 
condition which the Gangetic delta presented, when, in the latitude of Calcutta, the older 
alluvium, now about 65 or 70 feet below the surface and considerably therefore below the 
sea level, was nearly the height of the present surface and beginning to receive those ac¬ 
cretions of fiuviati'le and lacustrine deposits which now constitute the 70 feet of newer 
deposits whereon Calcutta stands, as before shown. This is precisely the condition of the 
Irawadi delta, and a downward movement, with a corresponding development of fluviatile 
beds, is all that is required to create a strict parallelism between the two deltas. For cor¬ 
responding development I might perhaps rather say consequent development, as the deposi¬ 
tion of any thickness of these fluviatile beds is proportionate to the subsidence of the area 
occupied by them, hence their absence in any force, over any elevated area occupied by the 
older group. At the same time I do not wish to he understood as denying that the flood 
waters which cross the country leave no deposit, hut only as insisting on the superficial 
and I may say insignificant development of this group in Pegu, from the reasons above given. 
When the entire country is composed of the older clay a thickness here and there of a 
few feet scattered over the surface and that after a very sparing fashion, scarcely deserves com¬ 
parison with the extensive and thick deposits of Gangetic alluvium. In the river hanks a 
couple of feet at most, and this I consider an over estimate, of surface soil is seen, the 
entire bank being composed of the old homogeneous clay. Farther removed from the 
main channel the deposition of river silt is even more trifling on two accounts; firstly 
from the more copious deposit of silt on the river bank, through the diminished velocity 
of the 5 C V CTfl°',vin s waters > a,1( l secondly from a cause not usually sufficiently home in mind. It 
may seem paradoxical, but the low level and small inclination of the ground is a serious 
obstacle to its becoming silted as I shall show. When a cross country “ spill” takes place 
and flood waters charged with sediment traverse a low country, deposition of course takes 
place, as when the floods of the Son abandoning their proper channel pour irregularly across 
the plains of Beliar, and in place of falling into the Ganges above Patna, effect an irregular 
discharge for themselves below it. Very different, however, is the case of a river running 
through so flat a country as the Irawadi delta, and possessing a rain-fall such as Pegu does. 
The first showers of rain fill the numerous “ engs” or depressions scattered over the 
country, and these gradually enlarging, submerge the country before the turbid floods of the 
river have risen to a similar height. In default of any effective drainage, the ground 
adjoining the rivers being higher than the flooded interior, the ordinary rain-fall of tlie 
district is usually adequate to produce this effect, but the low land skirting the hills, receives 
in addition considerable, though irregular supplies through streams which pouring out from 
the hills diffuse themselves over the country, and lose themselves in the plains. A vast 
quantity of sand is swept down and forms a sort of encroaching talus margining the plains, 
hut the somewhat depurated water mixed with the pure rain water ot the plains, together 
forms a body of water very limpid and free from sediment, though eventually often tinged with 
brown from decaying vegetable matter. The turbid waters of the Irawadi now rising, top their 
hanks, hut their course is soon arrested by the limpid water ot the plains and may often he 
traced holding on their course without mingling with the other by the contrast in colour 
the two bodies of water present, and this balance of power oi course tends powerfully to 
reduce the deposition of silt to a minimum over these inundated plains and restrict it to the 
immediate neighbourhood of the larger streams. 
In appearance the older clay of the Irawadi valley much resembles the older clay of 
Bengal, hut it differs from it in being very deficient in lime, and rarely containing, and then 
hut sparingly, these calcareous concretions or kunkur which give a distinctive character to the 
deposit in Bengal. It is a very homogeneous deposit throughout, but a thin dark band in it 
shows that it dips seaward, or to the south, at a greater angle than the surface oi the land, 
which proves that the process of elevation has been greater inland than towards the gulf 
of Martaban. This is quite in accordance with evidence oi an increased elevatory move¬ 
ment as we proceed up the coast, northward. Towards Cape Megrais no prominent signs 
