PART 1.] 
Alla rial deposits of the Irawadi, Sfc. 
23 
delta; since then a steady downward movement of the Gangetic delta has permitted the 
enormous accumulations of newer or Gangetic alluvium which covers so large an area in 
Bengal, whilst the future can alone disclose if any similar movement of depression will ever 
permit a corresponding accumulation of Irawadi alluvium in the delta in Pegu. That no 
such movement has taken place hitherto is clear from the absence of the newer deposits 
which would have originated in consequence of it, and moreover the proofs of a general 
elevation are, as I shall show, sufficiently clear and undeniable. 
Let us now consider how far the surface conditions which obtain in lower Pegu 
correspond with the supposition above advocated, of a somewhat recent elevation of the country 
from the sea (including, in the term elevation, the accessory agent of silting up), which, he 
the area rising or sinking, is always going on in so shallow and protected an estuary as 
the head of the Gulf of Martaban. The appearance of the bed of such an estuary as 
that in question, would, on its first elevation above the sea, he that of a dead level regarded 
as a whole—merely furrowed here and there by such channels as the drainage action of the 
retreating waters would inevitably carve out in a plain of soft easilv-removable matter. An 
exception to this dead level character might here and there exist either in the shape of banks 
of sand or other accumulations produced by currents; or depressions in the general surface 
produced either by the locally increased set of currents preventing the deposition of sediment 
or their absence altogether checking the delivery over particular localities of even the finer 
sedimentary particles. If we endeavour to follow the history of these suppositions de¬ 
pressions subsequent to their permanent elevation, and conversion into dry land, we shall 
thereby obtain a clue to the origin of the most prominent features at present of the Irawadi 
delta, viz., the presence throughout it of innumerable small “ engs” or lakes, the occurrence 
of some of different character, such as the Daga lake, and the existence of the curious 
isolated tract of newer alluvium, lying south of Pantanau. It is clear that in such a case 
as that supposed above, one of three results must happen to any depressions which the 
newly elevated surface may present. If the depressions are of small extent and of a shallow 
character, they will be converted into small lakes or “ engs” in the rainy season, and he 
more or less dried up and converted into grassy plains, such as are commonly seen in Pegu, 
with a swampy navel perhaps in the centre, during the dry season. If the depression is of 
larger dimensions, or receives a larger supply of water than evaporation can dispose of, it 
drains itself naturally into the nearest or most accessible drainage channel in the country, 
and this appears to be the case of the Daga lake. 
Should again the depression he extensive, and, as its existence might he held to render 
probable, it should he intersected or connected with one of the main drainage channels of 
the country, it will in such a case be silted up by repeated accessions of flood waters charged 
with sediment, and this appeal's to he the origin and history of the oasis-like tract of newer 
alluvium near Pantanau, which has all the aspect of being an extensive trough-like depression 
in the original surface of the land, lying in the course of two of the largest branches of 
the Irawadi, and in consequence speedily silted up to the level of the surrounding country 
by its waters. 
The difference between this case and the last is one it may be said of degree, but 
an aboriginal diffei'ence of level, though merely one of degree, produces exactly opposite 
results. A moderate depression, such as the Daga lake (even cceieris paribus and in 
this case the ground surrounding it is the higher), would, during the floods, as a rule, 
discharge into the nearest river, whilst a greater depression, like the Pantanau trough, would, 
during floods, never discharge into the river, but always itself be the recipient (till silted 
up) of the waters of the flooded stream. 
The Daga lake may he now briefly noticed as it forms a curious feature in the district 
1 am describing. The Daga lake is an annular piece of water situated on the west hank 
of the Daga river, 25 miles north-west from Pantanau. Its shape is irregularly oval, 2f- miles 
long, and varying from half a mile to a mile in width. It discharges its surplus waters into 
the Daga river by a short channel of about £ of a mile in length, hut from always remaining 
full is probably as deep as the channel of the Daga river itself. It is economically valuable 
as a fish preserve, and an account of the annual drawing of the lake is given by the 
late M. O'Riley in the Journal of the Asiatic Society, Bengal. M. O’Riley speculates on 
the mode in which it has been formed, but as he refers it to some vague intestine movement 
of the neighbouring strata, I am unable to agree with his conclusions. Did such a piece of 
