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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 25, 



by a sudden bend to the south, finds an exit for itself into the plains. 

 These valleys are, in the country with which I am acquainted, termed 

 Dun, while in Nepal, according to Mr. Hodgson, they are called 

 Mari. 



I may here mention, that with these valleys has been confounded 

 by some writers a totally distinct tract, locally called Tarai or Tari- 

 yani. Along the southern edge of the outer hills extends a band of 

 ten miles or so in breadth, usually covered by forest, and remarkable 

 for its utter want of water, All the minor streams as they leave the 

 foot of the hills are rapidly absorbed and disappear in the sandy and 

 shingly deposits that there prevail, and wells have to be sunk to a 

 great depth before water can be met with. The surface-slope of this 

 absorbent band is very considerable near the hills, but rapidly dimi- 

 nishes as we recede from them ; and we usually find that at a distance 

 of from ten to fifteen miles the character of the country changes rather 

 suddenly, the extreme dryness of the forest-belt being succeeded by 

 a line of swamp, clothed by a thick growth of reeds and grasses ; this 

 is the Tarai. It has been usually supposed that this swampy tract 

 was formed by an actual depression in the general surface of the 

 country ; but this seems to be altogether an erroneous idea, the truth 

 being that along this line the drainage of the higher country beyond 

 breaks out in copious springs which collect into swamps, in some 

 small degree, perhaps, from artificial obstructions to their outflow for 

 the purpose of utilizing the water for irrigation, but chiefly, I con- 

 ceive, from the small slope of the country, which can only amount to 

 a few inches in the mile for a distance of many hundred miles from 

 the sea. We accordingly see that this peculiar feature of the plains 

 immediately along the outer hills is confined to the country to the 

 east of the Ganges, the general level of which is considerably lower than 

 that to the west of that river. The dry band of country is, I pre- 

 sume, a great talus of coarser matter that has been formed along a 

 former line of coast, covering a deposit of finer and less permeable 

 silt, just as appears to be usual now ; the surface of the former being 

 naturally more inclined, of the latter almost horizontal, and the drain- 

 age of the whole of the upper portion being brought to the surface 

 along the line of union of the two. 



The Siwalik Hills seem, with hardly any exception, to have a well- 

 defined existence along the whole of the chain, from the Sutluj to the 

 meridian of Calcutta, running in a tolerably regular line, and presenting 

 much the same general features close along the southern edge of the 

 general mass of mountains. It so happens, however, that at the par- 

 ticular place where my examination took place, these hills are ex- 

 ceedingly ill developed ; and as I could nowhere find or hear of any 

 fossil remains among them, I did not think it worth while to devote 

 so much of my already very limited time as would have been neces- 

 sary for such a purpose to an attempt to unravel their obscurities, 

 which after all would most probably have been unavailing. I am 

 consequently unable to offer any fresh information as to the age of 

 these strata which have hitherto been supposed to belong to the 

 Miocene Period. 



