Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/497

1872.] 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 limestone 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 fragments), 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 flowed over it; nor was there any saline efflorescence.

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 Royal 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 inquiries, 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