182 Memorandum on the Irawadi River. [No. 2, 



more, and the surface velocity will be increased to upwards of o\ 

 miles per hour. Even admitting that the mean depth may have 

 been three feet, the discharge would still be under 3,000 cubic feet. 

 But as a stream with a mean depth of three feet, and a current of 

 5|- miles per hour, would be almost, if not quite, unfordable, a volume 

 of 3,000 cubic feet may be considered as the extreme discharge of the 

 Irawadi at Moong Khamti, consistent with Wilcox's observations. 



18. If this determination is correct, and I do not see how its 

 accuracy can be disputed, what has become of the Tsanpu, the great 

 river of Tibet ? The following measurements of the Brahmaputra 

 and its tributaries will probably assist in determining this point : 

 On 26th December, 1825. On 29th March, 1S26. 



Dihong (Bedford) 56,564 cubic feet. 



Dibong „ 13,100 



Joint stream ... 69,664 86,211 



Brahmaputra (Wilcox) 



at Saduja 19,058 33,965 



Total discharge ... 88,722 120,176 



On comparing the discharge of the Dihong with that of the 

 Dibong and Brahmaputra, the only natural way of accounting for 

 its immensely superior volume is by supposing that it must be fed 

 by some large stream from beyond the Himalaya. No accounts of 

 Cis-Himalayan drainage calculated from the data supplied by the 

 measurements of the Brahmaputra and Dibong would give a greater 

 discharge than 20,000 or at most 25,000 cubic feet. The question 

 then arises whence comes the other large volume of 30,000 cubic 

 feet of water, to which the only obvious reply is " from the Tsanpu 

 Eiver of Tibet beyond the chain of the Himalaya." The lower 

 course of the Tsanpu, where it breaks through the mountains, is 

 unknown ; but from all the evidence collected by Wilcox, compared 

 with the small discharge of the Irawadi, and with the large volume 

 of the Dihong, the connection of the Tsanpu and Dihong Rivers 

 seem to me to be as clearly and satisfactorily established as any de- 

 duction can possibly be without absolute ocular demonstration. 



