PART 1.] 
Alluvial deposits of the lvawadi. fyc. 
19 
marsh close under the hills (trap) in which spots the soil often hears no inconsiderable 
resemblance to the “Rcgur”* or dark “ cotton soil” so extensively spread over Central and 
Western India. 
If we follow the river by its most direct course to the sea down the Bhagirathi we see 
the last of the older deposit or “ hunker” clay in the steep bluff of Rangamatia (“ stained 
earth”) over 100 miles as the crow flies above Calcutta. 
Below this to the sea all is Gangetic alluvium, which at Fort William, as revealed to us 
by the boring operations for an artesian well, is about 70 feet in thickness, resting on the 
denuded surface of the kunker clay, which is clearly indicated by the “ rolled hunker pebbles” 
strewn over it, and intersected at that depth by the bore. To consider, however, the older 
deposit, merely in its aspect as regards the Gangetic basin, excavated in it, is to neglect a 
great and important parz of its history, that is, the entire period dining which the great 
thickness of beds under Fort William, revealed by boring, of which it constitutes the highest 
member, were being deposited. It is here we require to bear in mind the difference I 
have insisted on, between the Gangetic group proper and this older group, for there 
appear to me to be no such cogent reasons why we should consider these beds as 
“ Gangetic" deposits involving thereby a depression of several hundred feet, when it 
seems a simpler solution equally supported by the facts of the case to regard them as estuary 
deposits accumulated during an upward movement of the land. The fragmentary condition 
of the matters brought up by the boring rod prevents any great weight attaching to the 
mere presence of lacustrine shells and carbonaceous matters at a great depth, as the enormous 
quantity of wood, vegetable trash and lacustrine shells, swept out to sea, from a tropical 
shore and forming in places matted rafts, must be quite adequate to leaving a lasting record 
in the marine strata formed in times past, no less than in those now forming in the Bay. It 
will hardly he contested that at no very remote period the sea bathed the southern slopes of 
the Himalayas and stretched from the Bay of Bengal to the Persian Gulf, and to this period 
during a rise of the land, and long prior to the very existence of the present Gangetic valley 
or drainage system, would I refer these deep-seated beds, one of the highest of which is the 
“ kunker ” clay which it has been the custom hitherto to regard as a Gangetic deposit. It 
may he so ; hut I have always held it to he marine on grounds quite independent of those 
suggested by the Fort William bore. 
I do not, however, wish to affirm that this kunker clay which in lower Bengal I regard 
as mtua may not elsewhere prove to exhibit fluviatile characteristics, since in the upper part 
of the Ganges valley, say above Chunar, beds intimately connected with it, certainly afford 
fluviatile indications, and such variability is to be looked for in a deposit accumulated under 
such conditions as I have surmised; for supposing an equable elevation to take place over 
the whole area, still the accumulation of the coarser beds near the centres of supply of sedi¬ 
mentary matter, will be more rapid than that of the more remote, and they will consequently 
begin first to exhibit marks of fluviatile action as the sea or estuary shoals, whilst no such 
indications will be afforded by the others deposited in deeper water, and this appears to me a 
natural explanation of the fact of fluviatile beds occurring in the central and upper portion of 
the Ganges vallej', in intimate connexion with the kunkery clay which itself nowhere exhi¬ 
bits any similar indications. 
The reason, apart from any other considerations, which has mainly induced me to regard 
the old kunker clay, of lower Bengal at least, as a estu y r y deposit, is finding it high up on the 
flanks of Patarghatta hill, which rises somewhat abruptly from the alluvial plains close to 
the river, some few miles above Rajmahal. At the time of my visit, the clay was being 
worked in this position for lime, the kilns being placed near the foot of the hill for the con¬ 
venience of “ tipping” the “ kunker” clay down to them. The occurrence of the clay at this 
* An opinion 1 onco expressed regarding the probable derivation of t.ho “Regw“ from the destruction of 
decaying trap rooks, or some crystalline rookB of similar composition, received curious confirmation daring my exa¬ 
mination of Kast.om I’rome. 1 there heard repeatedly mentioned a certain hill of “black earth’’ which the Burmese 
described as forming a curious and isolated feature in the district. Nothing like “Kegur” had ever occurred to 
me, nor were there to my knowledge any rooks in the district, oxccpt miocenc sands and days, whieh did not seem 
likely to present the appearance described, on reaching the locality, however, X found not one only, but three 
isolated patches, or three separate hill tops of black earth, in every respect a veritable Rcgur, being the decom¬ 
posed surface soil of what 1 at first regarded aB a trap cap to the hill, hut which the last examined locality conv incod 
me was a bedded trap ash, subordinate to the beds including it, aud which happened to form tile summit of the three 
hills capped by the ” black eanli ’ m question. 
