1856.] Beport on the Magnetic Survey. 5 



Khosia hills. I followed the course of the Mahanuddy, Ganges, 

 Megna, and Soormah rivers, whilst my draftsman went by the Teesta 

 in order to make a plan of the river.* 



"We arrived at Sylhet September 23rd, and at Cherrapunji Sept. 

 29th. 



After visiting the different places of particular geological interest 

 near the Southern slope of the Khosia hills, and taking a series of 

 angles to determine the positions of spurs descending from the 

 plateau of Jynteah,* we passed through the interior of the Khosia 

 hills and descended into the valley of the Brahmaputra at Gowhatty. 

 As the conditions were here particularly favourable for calculating 

 the discharge of water in the Brahmaputra, the river passing through 

 a channel very well defined and pretty regular, we tried to determine 

 its amount. 



I found, per second, 



318,200 cubic feet during the time of low water. 



894,700 cubic feet during the time of high water. 



A detailed account of the operations connected with this deter- 

 mination is given in the latter part of my report.f 



We are now visiting the Northern part of central Assam near the 

 Bhootan frontier, the Assistant, Mr. Adams and the draftsman, 

 Abdool, are on their way to Jypore to see the coal and lime formation, 

 at Namding. Their directions are to go from thence by the Boree 

 Dihing and Noh Dihing to Sudeiya, and thence to Gowhatty. 



II. — Magnetic Observations. 



At Darjiling a complete set of magnetic observations was made 

 immediately after our arrival in Sikkim from the 15th to 17th of 

 April, and a second series after our return from the Nepalese 

 frontier at the end of July ; on the latter occasion three little houses 

 of bamboo were built in order to protect the instruments for com- 

 parative observations on the daily variations. 



2. At Tonglo complete observations from the 12th to 15th of May. 



* This plan will also be added to the next report, it is now in the hands of Capt 

 Thuillier, with the plan before mentioned. 



t A section of the river 1 : 1000 and a plan 1 : 5000 added to the report. 



