1879.] Discharge of large Rivers in Assam. 5 
The first river measured was the Subansiri. The method of proce- 
dure was as follows, and the same method of work was adopted for all the 
other rivers : 
A gauge-post was planted in the bed of the stream to note the varia- 
tion in level of the water during the operations. Four parallel lines were 
laid out across the river, at a perpendicular distance apart of 758 ft., 
the shore portions of the lines being marked by flags (vide fig. 1). 
Fig. 1. 
Base lines A B and C D were measured, and on a plane table a 
chart was made on the scale of 70 feet = 1 ineh showing the lines of flags 
and the margins of the river. The section was obtained in the following 
manner : 
A small dug-out (canoe) was anchored at (a) and the cable eased off 
until the observer (myself) in the boat was exactly on the upper or first 
line AC. A signal was made to an assistant stationed with the plane 
table at B or D, who at once cut in the position of the observer in the boat 
on the line AC. Soundings were then taken, and the boat let down to the 
2nd line or upper line of the “ Run.” ‘The position of the observer in the 
boat was again cut in and soundings were taken ; and so on for the remain- 
ing two lines. The boat was then hauled up, the grapnel raised, and a new 
position (@,) taken up. 
It was found that in most cases, the line joining the four sounding sta- 
tions obtained from one anchoring position, closely agreed in direction with 
the surface flow of the water at that part of the river. 
The instruments for measuring velocities were discs of wood 8 in. 
diameter and 7 in. thick, marked by a little mass of cotton 
wool thrown over a peg standing upright in the centre 
of the dise (fig. 2), Also tin tubes, 1 in. diameter, closed 
at one end, varying in length from 23 to 10 ft., containing 
enough water to sink the tubes, so that only 3 or 4 inches 
