Part 11 (1/2)
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 ma.s.ses of aquatic weeds, chiefly species of _Zannich.e.l.lia_ 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 sh.e.l.ls. 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_.
[Sidenote: 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 ill.u.s.tration 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.
[Sidenote: BORAX PLAIN.
_September, 1847._]
The whole of the plain is covered, to the depth of several feet at least, with white salt, princ.i.p.ally 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.
[Sidenote: BORAX LAKES OF TIBET.
_September, 1847._]
It has long been known that borax is produced naturally in different parts of Tibet, and the salt imported thence into India was at one time the princ.i.p.al source of supply of the European market. I am not aware that any of the places in which the borax is met with had previously been visited by any European traveller, but the nature of the localities in which it occurs has been the subject of frequent inquiry, and several more or less detailed accounts have been made public. These differ considerably from one another, and no description that I have met with accords with that of the Pugha valley. Mr.
Saunders[13] describes (from hearsay) the borax lake north of Jigatzi as twenty miles in circ.u.mference, and says that the borax is dug from its margins, the deeper and more central parts producing common salt.
From the account of Mr. Blane[14], who describes, from the information of the natives, the borax district north of Lucknow, and, therefore, in the more western part of the course of the Sanpu, it would appear that the lake there contains boracic acid, and that the borax is artificially prepared by saturating the sesquicarbonate of soda, which is so universally produced on the surface of Tibet, with the acid. At least, the statement that the production of borax is dependent on the amount of soda, leads to this conclusion. The whole description, however, (as is, indeed, to be expected in a native account of a chemical process,) is very obscure, and not to be depended upon. Mr. Saunders does not notice any hot springs in the neighbourhood of the borax; but in the more western district described by Mr. Blane, hot springs seem to accompany the borax lake as at Pugha.
It is not impossible that the three districts in which the occurrence of borax has been noticed, which are only a very small portion of those which exist, may represent three stages of one and the same phenomenon. The boracic acid lake may, by the gradual influx of soda, be gradually converted into borax, which, from its great insolubility, will be deposited as it is formed. On the drainage or drying-up of such a lake, a borax plain, similar to that of Pugha, would be left behind[15].
From Pugha, two roads towards Le were open to us. We might either return to the Indus, and follow the valley of that river throughout, or proceed by a more direct route across the mountains to join the road from Lake Chumoreri to Le, by which Mr. Trebeck had travelled on his way to Piti. As we knew that the Indus route would be surveyed by Captain Strachey, who was desirous of following the course of the river as far as practicable, we preferred the more mountainous road, and, therefore, on leaving our encampment at Pugha, on the morning of the 23rd of September, we continued to ascend the valley of the little stream, on the banks of which we had been encamped. For the first two miles the plain was nearly level, and similar in character to what has just been described, hot springs being observed at intervals.
[Sidenote: SULPHUR MINE.
_September, 1847._]
Two miles from our encampment, we stopped and examined the spot whence sulphur is obtained, at the base of the mountain slope on the north side of the valley. Ascending a few feet over a loose talus of s.h.i.+ngle, which skirted the bottom of the hill, we found two narrow caverns in the slaty rock, apparently natural, or only a little widened by art, roughly circular, and less than three feet in diameter at the mouth. One of these caverns continued a long way inwards, nearly horizontally, but it contracted considerably in diameter, and was so dark that we could not penetrate far. The rock was princ.i.p.ally gypsum, interstratified with very friable mica-slate. Sometimes the gypsum was amorphous and powdery, at other times in needles two or three inches long, perpendicular to the strata of slate. The sulphur was in small quant.i.ties, scattered among the gypsum, and was more abundant in the lower beds. It was frequently in very perfect crystals, not, however, of any great size.
The air which issued from these funnel-shaped apertures was very sensibly warm, and had a strongly sulphurous odour. Unfortunately, we had not antic.i.p.ated the necessity for observing the temperature, which was not by any means oppressive, and was only remarkable in contrast with the extreme cold of the external air.
In the neighbourhood of the sulphur-pits, the hot springs along the course of the stream were very numerous, evolving much gas. A little higher they ceased altogether, and the upper part of the plain was without any springs, as was evident from the quant.i.ty of ice by which it was covered. For more than a mile it was a dead level, and very swampy; but afterwards the valley became gently sloping and gravelly, the little stream being often hidden under the pebbles. Large boulders of the same granite which we had observed the day before, were scattered over the surface. The vegetation in this valley was extremely scanty, a few scattered tufts of _Dama_, and some shrubby _Artemisiae_, were occasionally seen, but the herbaceous vegetation had been almost entirely destroyed by the intense morning frosts, which had for some time been of daily occurrence. On the latter part of the day's journey the rock on the mountain-side changed from mica-slate to gneiss, of which very lofty scarped cliffs rose abruptly on the right hand. We encamped on a level spot, after ten miles of almost imperceptible ascent.
Next morning we continued to ascend the valley, which was now very rugged, from ma.s.ses of boulders, which were heaped one on another to a very great thickness. The stream had cut for itself a narrow channel, nearly a hundred feet in depth, the walls of which were entirely composed of huge incoherent ma.s.ses of rock, all more or less angular.
A walk of three miles brought us to the crest of the pa.s.s, which was nearly level and gra.s.sy for about a mile; its elevation was about 16,500 feet. The pa.s.s (Pulokanka La) is a very deep depression in the axis of the chain, which runs parallel to the left bank of the Indus, separating the waters tributary to that river from those which join the Zanskar river, some of the feeders of the latter springing from the valleys on the western slopes of these mountains. The hills right and left of the pa.s.s rise very boldly into rugged ma.s.ses, contrasting strongly with the level plain which const.i.tutes the pa.s.s, in which the watershed is scarcely perceptible.
[Sidenote: SALT LAKE.
_September, 1847._]
From the pa.s.s the descent was considerably more abrupt than the ascent had been. The valley to the right was bare and stony, watered by a small streamlet, which had, as on the eastern face of the pa.s.s, cut a deep channel for itself among boulders. On descending, we turned gradually to the right, and a lake by degrees came in view, towards the southern extremity of which the road advanced over undulating hills of fine clay, full of fresh-water sh.e.l.ls, almost entirely of one species of _Lymnaea_, of which the specimens were extremely numerous.
This lake is the Thogji Chumo of Mr. Trebeck, who travelled along it on his journey from Le to Piti.
[Sidenote: FOSSILIFEROUS CLAYS.
_September, 1847._]
I was much surprised, and not a little pleased, to find that the clay-beds contained fossils; as, except on one occasion in Piti, where I found one or two specimens of a small _Planorbis_, I had in vain sought in the clayey beds for any trace of organized beings. Here, however, sh.e.l.ls were in prodigious abundance, and as the species was a large one, they were very conspicuous. The clay formation was horizontally stratified, and quite impalpable. The uppermost beds were at least a hundred feet above the level of the lake; and as the valley by which we descended was in its lower part almost horizontal, the lacustrine beds extended to a considerable distance from the lake, forming a slightly undulating surface, over which the road ran.
After reaching the banks of the lake, the road kept its eastern sh.o.r.e throughout its whole length, which was about three miles, and we encamped close to its north end, on the edge of a level salt plain.