1873.] DREW UPPER-INDUS BASIN. 443 



is here very high on account of the small amount of precipitation. 

 Over all the country to be treated of some of the agents which pro- 

 duce alluvial deposits act with great intensity. Frost occurs in 

 winter over the whole ; in parts it occurs in summer as well as in 

 winter, the winter temperature of the loftier portions being exceed- 

 ingly severe. Tbe dislocation, or disjointing, and disintegration of 

 rocks goes on rapidly. The season at which the greatest movement 

 of material occurs is the spring ; at that time the fall of masses from 

 the cliffs, the sliding of material in company with snow-slips, and 

 later the rush of torrents laden with debris, arrest the attention, 

 and often enough the steps, of the traveller, and would, I think, be 

 enough to convince the most sceptical that he has in action before 

 him the very agencies that produced the ravines and valleys he is 

 traversing. 



I have found it to be most necessary carefully to classify the in- 

 stances of alluvial deposits met with, to refer each, not only in a 

 general way to the agency that caused it, but to the particular form 

 and degree of that agency ; failure to do this will almost surely lead 

 both to erroneous description of the facts and false results of induc- 

 tion. I do not pretend to much that is new in the classification now 

 to be given ; for each kind of deposit has often been observed in 

 other countries ; but the special character here put on is worthy of 

 attention. 



First, Loosened material. — This is simply the rock in that state to 

 which the action of the weather on the surface has brought it, being 

 still unmoved. The common form is a rugged surface made up of 

 masses of disjointed rock, with but little smaller stuff between them. 

 In other parts the disjointing has been such as to cover the whole 

 surface with comparatively small loose angular stones ; while a third 

 form, where the rock is shaly, with harder beds, as of sandstone, 

 interstratified, is a mixed surface of stones and mud. In Ladakh the 

 absence of vegetation leaves all this open to view ; and the sight is 

 apt to suggest, to an untrained eye, causes quite unfitted to account 

 for the simple facts. 



Second, Taluses. — These are the heaps of material which has 

 fallen from crags and cliffs, and lies at the foot of them in slopes, 

 not having been transported by streams, simply lying beneath its 

 parent rock, where its own weight brought it, aided, may be, by snow- 

 slips in those cases where rock and snow have taken the same course 

 in falling. These taluses are well known to those familiar with the 

 mountains of our own islands : at Wastwater, in Cumberland, is a 

 very fine example of them ; that lake is edged on its south-eastern 

 side by a line of talus that continues for miles, fallen from the cliff 

 that towers above. 



The material of a talus lies at the natural limiting angle of slope, 

 which may vary somewhat according to the nature of it, but is ge- 

 nerally near 35°. 



The above description will apply to all ; but there are two or three 

 special forms put on by taluses which are worth a few words. 



Fig. 1 shows an ordinary talus : in this the material coming from a 



