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



more, and fche surface velocity will be increased to upwards of 5^ 

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

 been three feefc, 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 

 5j 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 Ivhamti, 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 Tsánpú, the great 

 river of Tibet ? The following measurements of the Brahmaputra 

 and its tributaries will probably assist in determining this point : 

 On mth December, 1825. On Zdth March, 1826. 



Dihong (Bedford) 56,564 cubic feet. 



Dibong „ 13,100 „ 



Joint stream ... 69,66á 86,211 



Brahmaputra (Wilcox) 



atSaduja 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 Tsánpü 

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

 course of the Tsánpü, 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 Tsánpü and Dihong Rivers 

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

 duction can possibly be without absolute ocular demonstration. 



