GHOLOGICAL MAGAZINE. 
NEW RSERIES: “DECADE Vo" VOLE Ville 
No. VOB eye 1910. 
Oe EGSEIN EASE, PAGE En @ rene S5 
I.—Erosion and Deposrrion BY THE INDUS. 
By Artuur Hixtz, C.1.E., Assistant Secretary P.W.D. Bombay. 
[Communicated by the Rev. E. Hill, M.A., F.G.8., The Rectory, Cockfield, 
Bury St. Edmunds. | 
‘67/T\HE Indus has been eroding severely on the right bank, about 
30 miles higher up than the erosion which I told you threatened 
the railway at Rohri on the left bank. The chord of the curve of the 
bank attacked was over 2} miles long, and the erosion at the apex 
would be as much as 100 feet a day: it amounted to 3400 feet in 
forty days. It has given us a good deal of trouble, as with a big 
breach here the water would travel 120 miles before it would be 
forced back to the river by the hills on the edge of the deltaic deposits, 
and loop embankments of great length had hastily to be constructed 
behind the portions of the flood-embankments threatened with erosion. 
We succeeded with two loops, but with the third had a breach in the 
weak new loop; the men have been able to keep it from spreading 
more than 700 feet wide, and have since got it nearly under control. 
‘Tf the bones of the famous geological mule had been on the river 
bank, they might have been dropped down to the 60 or 100 feet 
depth to which the river erodes, and have had half a mile of deposits 
put down alongside them, and between them and the bank of the 
river; for these channels in bends eroded are filled up again equally 
rapidly when the river cuts across the chord. So your mule might 
have had 60 feet depth over him, and the half-mile of new silt along- 
side him, in three months. The construction of a square mile of new 
deposits, 60 feet deep, in about two months time, is of almost annual 
occurrence locally on the Indus. These are, of course, not [pure ? | 
silt deposits ; they are merely the land at the side of the river rolled 
over, as in ploughing. 
‘*« Pure silt deposits occur, where the river overtops its natural bank, 
and in side-channels of the river where the exits are getting smaller 
than the upstream ends. In the latter case considerable depths, 
15 feet or so, of pure silt are deposited in a month or two. 
‘Most silt probably goes on to the sea. The average discharge of 
the Indus during 1906, from June to September inclusive, was 
400,000 cubic feet per second. . . . The maximum quantity of silt 
observed in suspension was 2797 grains weight per cubic foot of 
water. . . . I have not worked out the quantity of silt for the year, 
but clay weighs about 120 lbs. a cubic foot. . . .” 
DECADE V.—VOL. VII.—WNO. VII. 19 
