1873.] DREW UPPER-INDUS BASIN. 451 



increase of fan-stuff, that the river and the ravine-stream both were 

 raising their beds ; then there will have been an interstratification of 

 the two deposits at the fan-edges as they were at successive epochs, 

 a lapping for a short distance of one set of alluvial beds over the 

 other. 



I have sometimes observed in section an interstratification such as 

 to suggest the above origin — beds of well-rounded materials and of 

 sand among the less-worn fan-stuff; for indeed the latter, being 

 nearer its source, is seldom thoroughly rounded. 



Perhaps I have not hitherto said enough as to the substance of the 

 alluvial fans. The form of them, indeed, depends but little upon its 

 character, though doubtless the slope is affected not alone by the 

 quantity of water that flows down, but also by the size of the masses 

 that are weathered off from the mountains and the facility with 

 they will further disintegrate. Some fans are made up of semi- 

 angular pieces of stone, of such material as hardened shale and slate, 

 of sizes seldom above that of an octavo volume ; others, that come 

 from granitic mountains, are made up of more or less rounded blocks 

 of granite, which are often as much as 4 feet in diameter; but among 

 these will be found gravel and sand of the same material ; in some 

 cases the material is such as to merit the description " unrounded." 



The crossing of such stony plains or slopes as these fans constitute 

 is a great feature in Ladakh travelling ; many a weary mile of rough 

 road unsheltered from either rain or wind does one pass over between 

 the villages or the halting-places, alternately scorched by the heat, 

 which is doubled by reflection from the bare stones, and penetrated 

 by the cold wind that rises as the day declines. 



We have hitherto treated of fans that are whole and unclenuded, 

 and have considered the formation of them in that complete form ; 

 now we have to trace the changed state that many of them are found 

 in, the result of the denuding-action they have been exposed to. 



What would be the effect if the Nubra river changing its course, as 

 rivers do that flow over a level alluvial plain, should attack and eat 

 into the circumference of the fan we first looked at ? It would cut off 

 a segment, cut a cliff in the substance of the fan, which cliff would 

 increase in height as the action proceeded inwards. At the north- 

 western end of the line of fans opposite Leh just such a thing has 

 occurred ; there a cliff has been made by the river Indus in the sub- 

 stance of some of the fans, from 50 to 100 feet in height. 



The annexed diagram, fig. 8, will illustrate this and other cases. 

 The fan had formerly extended from a to d, where it joined the 

 river- alluvium flat d, e ; but the river has in one of its lateral 

 deviations cut it back from d to c, and made a low cliff at e, and 

 then retired and left its alluvium on that space. 



Where the river cuts deeper back, so as to make a higher cliff, and 

 where there is a considerable volume of water flowing over the fan from 

 the side ravine, more complicated results follow, the nature of which 

 I must describe somewhat in detail. We will suppose the river to have 

 cut its way back as far as b, and made a cliff in the fan a hundred 

 or two hundred feet in height. The ravine-stream discharged from 



