1872.] HENDEESON TAEKAIS-D SAND-PITS 1510. 403 



of our progress (15 to 30 miles a day), my notes were necessarily 

 very imperfect. I have formed, however a theory regarding them, 

 which Mr. Etheridge considers feasible ; and he has asked me to give 

 the result of my observations to the Geological Society. 



After crossing the Karakoram watershed, at an altitude of 19,600 

 feet above the sea-level, we came to a plateau elevated about 18,000 

 feet above the sea, and which sloped very gently towards the plains 

 of Central Asia, with the Kuen-Lun range, 20,000 to 24,000 feet 

 high, intervening between us and these plains. 



After two days' march (50 miles) we came to a number of lime- 

 stone ridges, rising from 200 to 500 feet above the plain, with wide 

 valleys between them ; and in one of these valleys, between the 

 camps named Luk Zoong and Tarl Dat, I first noticed the circular 

 pits. The valley was about eight miles long, and from half a mile to a 

 mile wide, and had a very gentle slope. The surface of the ground 

 consisted of sand, clay, and gravel (formed mostly of angular frag- 

 ments), in varying proportions, and for miles was indented with 

 pits, all very regularly circular in shape ; they varied in diameter 

 from six to eight feet, and were from two to three feet deep. The 

 sides sloped regularly towards the centre ; and some of them were 

 partially filled up with sand, which seemed to have been blown by 

 the wind. The intervals between the pits were about equal to their 

 diameters ; and there were no raised ridges round their margins. 

 The soil was quite dry ; and there were no signs of water having 

 fiowed over it ; nor was there any saline efiiorescence. 



At the head of the valley, and where side-valleys debouched, there 

 were water-channels, which were in a few places moist. All the 

 country round is as nearly as possible absolute desert. The little 

 rain or snow which falls in these elevated and arid regions evidently 

 finds its way under the surface of the ground in this particular 

 valley. 



At the end of the march, near Tarl Dat, lat. 35° 15' N". and long. 

 79° 30' E. (according to Hayward's map, published in the ' Journal 

 of the Eoyal Geographical Society'), the ground sloped much more 

 rapidly, and a series of springs issued from the soil and supplied a 

 large ice-bed twelve to fifteen miles in diameter. Here the pits 

 were again seen, but were less regular in size and few in number. 

 Many of them had a mound of dry frothy mud projecting from them 

 to a height of two or three feet. A very intelligent Sikh trader, who 

 had repeatedly traversed this region, told me, in answer to my in- 

 quiries, that after rain these pits at Tarl Dat frothed like yeast. 



After three marches (50 to 60 miles) we came to the Karakash 

 river ; and in the extensive marshes (half a mile to a mile across) 

 which intervene between the river and the Kuen-Lun ranges to the 

 north, we again saw the circular pits ; but here they were partially 

 filled with strong brine, and some were incrusted with common salt, 

 which our followers collected for use with their food. 



I find no mention made of these pits by Hayward, although he 

 travelled over the same ground ; but Mr. Shaw, in his book entitled 



