426 



The Physical Condition of 



[Oct. 



Upper Assam, as may be expected from these views, is an extensive 

 alluvial basin; regarding which, much depends on the accuracy of our 

 general and particular observations, as it brings us at once to the main 

 object of enquiry — the history of tiie tea plant and the circumstances 

 in regard to soil under which it exists. 



In considering the extent and nature of this basin, we are at once 

 struck with the peculiarity of a perfect plain about eighty miles long, 

 and forty broad, surrounded by lofty mountains and invaded by four 

 enormous rivers, besides six or seven smaller ones, the least of which 

 is as large as the greatest river in England. 



These streams are so many great channels, by which nature conveys 

 into the valley, the productions of the mountains ; and it is only neces- 

 sary to mention the direction from whence a few of the principal 

 streams are derived, in order to be prepared to find, in the natural his- 

 tory of this romantic and singular spot, a greater variety of objects 

 than a similar extent of any less peculiar situation could be expected to 

 afford. 



The first of these great rivers is the Dihong, which enters the valley 

 by a narrow defile in the Abor mountains about twenty-five miles N.W. 

 of Suddyah. Every circumstance seems combined to render the Dihong 

 liable to sudden, or at least excessive periodical inundations, its hydro- 

 graphical basin extending amidst snows, parallel to the equator from 

 the 82° to the 93° of longitule, along the elevated plateau of the 

 Himalaya.* 



The first rise of this river takes place in the beginning of March,and 

 amounts to about fifteen feet, said to be occasioned by the melting of 

 the snow. Towards the middle of April, there is a general subsidence 

 of about ten feet, and the river retains something more than its ordi- 

 nary level, until the periodical rains set in, when the inundations com- 

 mence, the river then begins to rise at Gowahatti, where it attains in 

 July and August a height of forty feet above its level during the dry 

 season. 



The second great branch of the Bramaputra— the Dibong, enters the 

 valley by a similar defile to that of the Dihong. Between the defiles 

 of these two rivers, which are not above 15 miles apart, there is a re- 

 markably abrupt and picturesque mountain, terminating in three peaks, 

 on the highest of which snow lies for two-thirds of the year. The 

 source of the Dibong is unknown, but it must approach, if it does not 



* According to Malte Brun the peculiarity of the inundations of the Nile depends on ita 

 course being extended from east to west within the tropics. The inundations of such 

 rivers are higher but less sudden than those of rivera running parallel to the meridian 

 like the Suban-Shieree. 



