176 Memorandum on the Iraioadi River. [Xo. 2, 



3. The following are the dates of minimum, or lowest level: 



— 



Thayetmyo. 



Peome. 



Henzadah. 



1856 

 1857 

 1858 



7th April. 

 20th March. 



10th March. 

 31st March. 



14th April. 

 &th March. 



3rd May. 



4. I have no means of comparing the monthly rise of the river 

 with the monthly fall of rain, as the only rain registers which I have 

 been able to procure are those of Rangoon. The diagrams, however, 

 show that an early setting in of the monsoon is accompanied by an 

 early rising of the river. For instance, there was no rain in April 

 1857, when the first great rise of the river was delayed until the 

 20th June. During the present year, however, there was a fall of 

 more than six inches of rain during April, and accordingly the 

 Irawadi attained its first great rise on the 1st of June or just three 

 weeks earlier than in the previous year. 



5. The diagrams also show, by the exact correspondence in time, 

 as well as by the relative correspondence in quantity, of the alternate 

 risings and fallings both at Prome and at Henzadah, that the annual 

 swell of the river is mainly due to the rain-fall in its upper course. 

 Thus, the pulsations of the river at Henzadah generally take place 

 just one day later than at Prome. This coincidence in the times 

 and quantities of the swell and fall of the river above the Delta might 

 have been inferred from the narrowness of the strip of land drained 

 by the lower Irawadi compared with the greater breadth drained in 

 its upper course. 



6. These diagrams further show the very small amount of rise 

 that is due to melted snow, and consequently the limited extent of 

 the snowy mountain range drained by the Irawadi. As this is a 

 point of some interest with reference to the still disputed question 

 of the connection of the Irawadi with the Tsanpu River of Tibet, I 

 now give the details of the rise and fall of the Irawadi for every ten 

 days between the date of lowest level, and that of the first great rise 

 due to the setting in of the Monsoon. 



