AN INDIAN RIVER AS A LAND-MAKER. 55

tide, from 1 to 2 inches. In the delta the current seldom sufficesto carry the burden of its silt, except during the rains, and sodeposits it. 1

In Lower Bengal, therefore, the Ganges enters on the third Thirdstage of its life. Finding its speed checked by the equal level Indian of the plains, and its bed raised by the deposit of its own river, assilt, it splits out into channels, like a jet of water suddenlyobstructed by the finger, or a jar of liquid dashed on theground. Each of the new streams thus created throws outin turn its own set of distributaries to right and left. Thecountry which their many offshoots enclose and intersect formsthe delta of Bengal. The present delta of the Ganges may be The deltataken to commence at a point 1231 miles from the source of of Ben g al -the river, and 326 from the sea by its longest channel. At thecommencement of the delta of the Ganges the head-waters ofthe Hugh break off, under the name of the Bhagirathi', fromthe parent channel, and make their way south to the sea. Themain volume of the Ganges pursues its course to the south-east,and a great triangle of land, with its southern base on the Bayof Bengal, is thus enclosed.

1 The following facts may be useful to observers in Bengal who wishto study the most interesting feature of the country in which they live,namely the rivers. Ten inches per mile is considered to be the fall whicha navigable river should not exceed. The average fall of the Ganges fromthe point where it unites with the Jumna at Allahabad to Benares (139 miles),is 6 inches per mile; from Benares to Colgong (326 miles), 5 inches per mile ;from Colgong to the delta-head, where the Bhagirathi strikes off (about135 miles), 4 inches per mile ; from the delta-head to Calcutta (about 200miles), also 4 inches per mile ; from Calcutta to the sea via the Hugh(about 80 miles), I to 2 inches per mile, according to the tide. The fallof the Nile from the First Cataract to Cairo (555 miles), is 6J inches permile ; from Cairo to the sea, it is very much less. The fall of the Missis­ sippi for the first hundred miles from its mouth, is i’8o inches per mile ;for the second hundred miles, 2 inches; for the third hundred, 2'30inches ; for the fourth hundred, 2-57 inches ; and for the whole section of855 miles from the mouth to Memphis , the average fall is given as 4)inches to the mile.

The following table, calculated by Mr. David Stevenson (Canal andRiver Engineering, p. 315), shows the silt-carrying power of rivers atvarious velocities :—

Inchesper Second.

3

6

12

24

Miles perHour.

0*170 will just begin to work on fine day.

0*340 will lift fine sand.

0*4545 will lift sand as coarse as linseed.

0*6819 will sweep along fine gravel.

1 '3638 will roll along rounded pebbles i inch in diameter.2*045 will sweep along slippery angular stones of thesize of an egg.