The hard conglomerate of the day before did not again occur, various forms of clay-slate being the prevailing rock. The steep slopes were, however, very frequently covered with a talus of angular fragments, which obscured the structure of the lower portions of the mountains, at the same time that it revealed the nature of the higher strata, which would otherwise have been inaccessible. Red and green jaspery rocks, very hard and brittle, were abundant, with various forms of greenstone, at times closely resembling syenite. These were evidently the same rocks as had been met with in the neighbourhood of Hanle, and along the river for some way below that town. Their recurrence here, therefore, tended to confirm what had for some time appeared to me to be the prevailing strike of these formations, namely, from S.S.E. to N.N.W.
After following the course of the Indus for about eight miles, we turned abruptly to the left, ascending a narrow gorge, in which a considerable stream flowed from the south-west. The slope was, from the first, considerable, and the course of the ravine very winding. Steep rocky cliffs rose precipitously on both sides, and generally approached so close to one another that their tops could not be seen. The channel of the stream was at first stony and quite bare, but after a mile bushes of the Myricaria became common, fringing the stream, but nowhere growing at any distance from it. These gradually increased in size and abundance, and at our camping place, three miles from the commencement of the ravine, they were generally small trees, many of them not less than fifteen feet in height, with stout erect trunks five or six inches in diameter.
The morning of the 21st of September was bright and clear, and intensely frosty, the unsettled weather which had continued since our leaving Hanle having quite disappeared. Our road still lay up the gorge, which had quite the same appearance as on the previous day. High precipices, or very steep banks, hemmed in the stream on both sides. Small trees of Myricaria still continued abundant in the immediate vicinity of the water; elsewhere, all was as desolate as ever. Some of these trees were not less than a foot in diameter; the trunk was generally very short, often branching within a foot of the base. At intervals there was a good deal of alluvium, partly in the shape of coarse conglomerate, partly a fine micaceous sand, filling up the recesses at the bends of the ravine. After three miles, the ravine suddenly expanded into a narrow plain, the surface of which was irregularly undulating, and completely encrusted with salt. As this plain was interesting in consequence of the production of borax, we encamped on the bank of the little stream about a mile from the end of the gorge, and remained stationary the next day in order to examine the nature of the locality in which the borax is found.
HOT SPRINGS.
September, 1847.
As the day's journey was a very short one, we arrived at the salt plain by eight o'clock A.M. The air was still quite frosty. While our tents were being pitched on a dry bank a little way above the stream, we proceeded to its bank, and were not a little surprised to find the water quite tepid, notwithstanding the extreme cold of the air. On procuring a thermometer, it was found to have a temperature of 69°. Advancing up the stream, we found that numerous hot springs rose on its banks, and sometimes under the water. The hottest of these had a temperature of 174°. From these springs gas was copiously evolved, smelling strongly of sulphur; and in their immediate neighbourhood the water of the little river had a faintly sulphurous taste, though elsewhere it was quite pure and good. The stream, which was perhaps twenty feet wide, was usually rather deep. Dense masses of aquatic weeds, chiefly species of Zannichellia and Potamogeton, grew in the water, and along the margins their dead stems, mixed with mud, formed immense banks, scarcely strong enough to bear the weight of a man, and yet seemingly quite solid. A small crustaceous animal was common among the weeds, but though I searched with care I could find no shells. The stream was full of fish, which swarmed among the weeds, and darted backwards and forwards in the tepid water in immense shoals. They were generally about six inches in length, and appeared to my inexperienced eye to belong to two or three species, all different from those which had been seen at Hanle. In the hottest water of the hot springs I collected three species of Conferva.
MYRICARIA TREES.
September, 1847.
The existence of the tree Myricaria in the gorges between Pugha and the Indus, which had appeared to us at the time very remarkable, was fully explained by the occurrence of the hot springs, and the consequent high temperature of the water of the stream, and was peculiarly interesting as an illustration of the influence of temperature upon vegetation. It may fairly be considered, I think, as a proof, that arboreous vegetation does not cease at great elevations in consequence of the rarefaction of the air, but only on account of the diminution of temperature which usually accompanies increased elevation. The trees of Myricaria, it must be observed, came abruptly to an end with the ravine, none occurring on the open plain. We cannot suppose that the trifling increased elevation caused their disappearance; it seems probable that the narrow walls of the gorge, by concentrating the heat, prevented its escape, and that, therefore, the temperature was more elevated than in the open plain, where the action of winds and free radiation combined to lower it. The occurrence of fish in the water of Pugha, at an elevation of nearly 15,500 feet above the level of the sea, is also very remarkable, and still more strikingly demonstrative of the same fact, inasmuch as it would certainly not have been very surprising that air at that elevation should, from its rarity, be insufficient for the support of life in animals breathing by gills.
At the gorge, where the narrow ravine expands into the lake plain of Pugha, the rock is clay-slate, but the hills which skirt the open plain are micaceous schist, varying much in appearance, often with large crystals of garnet, and crumbling rapidly to decay. On the surface of the plain lay many scattered boulders of a peculiar kind of granite, evidently transported from a considerable distance along the stream; and in all the central parts of the plain, a very remarkable conglomerate in horizontal strata, consisting of angular fragments of the surrounding rocks, cemented together by calcareous matter, was observed.
BORAX PLAIN.
September, 1847.
The whole of the plain is covered, to the depth of several feet at least, with white salt, principally borax, which is obtained in a tolerably pure state by digging, the superficial layer, which contains a little mixture of other saline matters, being rejected. There is at present little export of borax from Pugha, the demand for the salt in Upper India being very limited, and the export to Europe almost at an end.