1856.] Report on the Magnetic Survey. 23 



The geological map of the Khosia hills was continued from Nunck- 

 low to the valley of the Brahmaputra. 



V. — Remarks on some liydrographic observations. 



The velocity of the current in different streams has been fre- 

 quently measured and compared with the accumulation of deposits 

 and size of boulders, with the depth of erosion, etc. 



The quantity of the discharge has been determined in the Maha- 

 nuddy, the Ganges* near Rampore Bauleah, and the Brahmaputra 

 near Gowhatty. 



The Mahanuddy immediately below its junction with the Eatiang 

 had a discharge of 240 cubic metres per second, and near the village 

 of Sirsee below Malda 4,500 cubic metres per second, breadth 1,073 

 metres. For the Brahmaputra, the detail of the observations and 

 the results obtained are given in the following pages. 



Observations on the river Brahmaputra at Gowhatty, 



The form of the valley of the Brahmaputra near Gowhatty is 

 particularly well adapted for measuriDg the quantity of its discharge, 

 the bed of the river being well denned, and the mass of water 

 occupying only one channel. Besides, the station of Gowhatty being 

 close to the (left) shore of the river, I had the advantage of getting 

 much valuable information about the changes of the river in differ- 

 ent seasons from the inhabitants. I mention particularly Major 

 Yetch and Lieut. Craster, repeating my best thanks to them. 



The observations were made from November 21st to December 13th 

 the soundings November 28th and 30th, the determination of the 

 velocity November 29th to December 3rd. 



No. 1.— Breadth of the river. 



The breadth of the river was ascertained by measuring a base line 

 BE on the right shore and making a triangulation with a theodolite 

 reading 10' - by the vernier. 



* The observations on the Ganges have been sent to Calcutta, without the result 

 being copied out for the report. 



