58 
DECEMBER 1765. 
River is 22 miles/ the Course of which is from West to WNW, very different from 
the description given of it in the Maps.' 2 We were not permitted to land on the 
Northern or Assam side, all the way, there being several Chokeys placed; however 
we found means to lay down about io miles beyond the Bengali Frontiers, & in 
returning we coasted the Assam side near enough to inform ourselves of all the 
particulars which we wanted. 
This River must needs have a very long Course before it enters the Bengali 
Provinces, since 400 miles from the sea it is twice as big as the Thames. By 
measuring the Banks & c. I find that the Rains swell this River 32 or 33 foot. 
The Bengali Country extends 18 or 20 miles to the Eastward of Commerputa 
(the Frontier Town on the River) & afterwards as I am informed the Boundary runs 
in a Southerly direction towards Silet & Bermas. 3 However, that must be the 
Object of a future Survey, as we are now surveying the Countries to the Westw' 1 . of 
the Baramputrey. 
16 The Harrow Provinces begin about 12 miles south of the Baramputrey, & are 
bounded by the Rungjulee& Sosong Mountains 4 ; some of them are independent of 
Bengali. 
The 6th. returned to Gwalpara ; the next day employed in reducing & compiling 
the Surveys, & procuring Pilots & Hircaras for the Bisnee Countrey. 
P'rom the 8th. to the nth. employed in tracing the Bonaash & Birally Rivers 
from Jugygupa to the Frontiers of Assam & Boutan. I have mentioned some 
particulars concerning the Bonaash in page 12 & 13; the Birally or Barrally is a small 
River from Boutan which joins the Bonaash 12 miles above Jugygupa & has a 
Course from NW to SE. 
1 To the present boundary with the Kamrup district. The northern side is now part of the latter district, 
Kamrup marking the western extension of the Assam kingdom in the 18th century. 
2 in his * Memoir of Hindoostan ’ (p. 356) Rennell says: — “ On tracing this river in 1765, I was no less surprised 
at finding it rather larger than the Ganges, than at its course previous to its entering Bengal. This I found to be from 
the east ; although all the former accounts represented it as from the north ; and this unexpected discovery soon led to 
inquiries, which furnished me with an account of its general course, to within :oo miles of the place where Du Halde 
left the Sanpoo. I could no longer doubt, that the Burrampooter and the Sanpoo were one and the same river: and 
to this was added the positive assurance of the Assamers, ‘That then river came from the north-west, through the 
Bootan mountains.’ And to place it beyond a doubt, that the Sanpoo river is not the same with the river of Ava, but 
that this last is the great Nou Kian of Yunan ; I have in my possession a manuscript draught of the Ava river, to 
within 150 miles of the place where Du Halde leaves the Nou Kian, in its course towards Ava; together with very 
authentic information that this river (named Irabatty by the people of Ava) is navigable from the city of Ava into the 
province of Yunan in China.” 
I have quoted this passage at length, because it shows the acuteness of Rennell’s reasoning, and that he was the 
first to recognise the identity of the Brahmaputra with the Tsan-po of Tibet. The controversy has not even yet been 
settled by actual exploration, but Mr- Needham in 18*5-6 proved that the river that flows past Sama, in the Zayul 
valley, is not a tributary of the Tsan-po as had been supposed, but is continuous with the Brahmaputra at Sudiya. and 
as it had already been shown that the Tsanpo does not flow to the east of Sama, there is no doubt that it breaks through 
the Himalayas by the channel of the Dihang, the largest river falling into the Brahmaputra from the north. This 
passage, however, shows that even Rennell was liable to be misled by hearsay information, for the Nou Kian or Lu 
Kiang of Yunnan is the Salween, and not the Irrawaddy or ‘ river of Ava.’ 
For an account of the changes in the course of the river between the time of Rennell’ s Survey and 1809 see 
Buchanan Hamilton (Martin, History, Vol. Ill, p. 387 seq.). 
Burma. This boundary coincides with the eastern limits of the Garo Hills disrict. 
* i.e. on the north and south sides respectively. The Garo Hills were not entirely brought under control till 1873. 
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