Western Himalaya and Tibet / A Narrative of a Journey Through the Mountains of Northern India During the Years 1847-8

by Thomas Thomson

MOUNTAINS OF PITI.
August, 1847.

In the neighbourhood of Lari, the Piti valley is considerably more open than lower down. It had, indeed, been gradually expanding since we joined it at Lio. The mountains now recede considerably from the river, a long sloping surface of alluvium being interposed, which is at one time largely developed on the north side of the river, in which case the southern spur generally projects. A little further on, the northern mountains send down a projecting spur, and an open tract is seen to the south. The mountains behind the alluvial platforms rise very abruptly, and present towards the plain, steep, almost perpendicular slopes, which, from the peculiar nature of the rock, a very fragile slate, are covered by a steeply-sloping mass of débris almost to the top. This talus, indeed, on some of the cliffs behind Lari, seems to rise to the very summit of the ridges.

It is not easy to convey an idea in words of the mode in which these mountains are arranged, unless it is recollected that it is an universal rule that all mountains are ramifications of an axis, giving off branches on both sides, and that each branch is again divided in a similar manner, till the ultimate divisions are arrived at. All mountainous districts are in this respect similar to one another, and differ principally in the proportion borne by the altitude to the superficial extent of the ranges of which they are composed. An examination of the map will show that the axis of the range which lies north of the Piti valley, passes through the Parang pass, and in fact occupies the midway between the Piti and Parang rivers, terminating in the great bend of the latter, to the east of its junction with the Piti. The whole of this range is of great altitude, and it seems to rise in elevation to the eastward, no passage being known further east than the Parang pass. The primary branches of this chain, descending towards the Piti valley, are separated by considerable tributaries which discharge themselves into that river. In general, these lateral streams have, in the lower part of their course, very rugged rocky channels, but they rise rapidly, and, at a distance of a few miles from the main river, their ravines expand into open valleys, three or four thousand feet above its level. The ramifications of the primary branches are, as might be expected, in their upper part concealed among the mountains, but those near their termination abut upon the main valley, in a series of ridges separated by little streamlets. We have, therefore, as we ascend the Piti river, not a wall of mountain, parallel to its course, but a succession of ridges, more or less perpendicular to it, all descending from a great elevation, and rapidly diminishing in height. The result is necessarily a great degree of irregularity, the width of the alluvial belt varying much, while the direction of the ridges, and of the cliffs by which they are bounded, is constantly changing.

ALLUVIAL PLATFORMS.
September, 1847.

Leaving Lari on the 1st of September, we continued our journey up the Piti valley. The road lay partly on the platforms of alluvial conglomerate, and partly over the steep shingly talus which rested on the hills where they were not separated by alluvium from the river. One alluvial plain, about two miles from Lari, was well cultivated with the usual crops, the barley being quite ripe, the wheat very nearly so, the oil-seed and buckwheat out of flower, and the millet, of which there were only a few fields, still green. The platforms of alluvium have, in general, an irregularly triangular form, the base resting on the river, the apex at the termination of a mountain ravine, down which a stream runs. This stream, instead of bisecting the platform, usually runs in a hollow channel on one side or other between the mountains and the alluvium, and is, where practicable, carried off in small artificial conduits for the purposes of irrigation. The platforms always slope gently from their apex to the river, and they are generally cut off in a cliff at the lower end. These cliffs always show marks of stratification, sensibly parallel to the river, and the pebbles which the alluvium contains, are (and have been for the last two days) usually rounded.

I ought not to omit to mention, that I use the word alluvium merely as a convenient mode of expression, without meaning to convey an idea of the mode in which these beds originate. No equally suitable word suggests itself, and the phenomena occur so frequently, that it is necessary to have some short expression by which to describe them. The origin of these alluvia is certainly very puzzling. At first sight, in any particular spot, the most natural suggestion is, that they have been deposited under water, and probably therefore in a lake. Their occurrence day after day, notwithstanding the greatest changes of altitude, their enormous thickness in many places, and the peculiar position in which they occur, soon dispel this idea, and throw the observer into a maze of doubt and difficulty, at last leading him to the conclusion, that no one cause is sufficient to explain the highly variable phenomena which he observes, and that a lengthened series of patient observations will be necessary before the subject can be understood. These observations have yet to be supplied, but I believe I shall best serve future observers, by detailing as fully as possible the points which attracted my attention, without attempting for the present to speculate upon the causes of the phenomena. The suggestions which I have to offer to the reader, will be best understood when I have detailed all the facts upon which they are founded.

It is especially necessary to distinguish between three forms of alluvium, all of which have already occurred in Piti. These are, first, the fine clay; secondly, the platforms, such as I have described in the last paragraph; and thirdly, the enormous masses, which are without any definite limits, and do not seem referable to any present valley system.

POK.
September, 1847.

We encamped at Pok, a large village nearly nine miles from Lari. Here we found again an extensive alluvial platform, covered with much cultivation; and on the mountain ravine above the village there was a considerable grove of young juniper-trees. A week or two before, I should have considered them as scattered trees; now they had quite the appearance of a forest, so bare had the country been since crossing Hangarang.

West of Pok, our journey of the 2nd of September was over the alluvial platform, which continued for two miles beyond the cultivation of the village, gradually contracting in width by the encroachment of successive spurs, which at last advanced close to the river. The road now ascended by a short steep path on the mountain-side, to a higher level. At the base of this ascent there were a great many angular masses of limestone, evidently transported from the valleys behind. These fragments were very numerous, and many of them of great size. They continued abundant during a great part of the day, but no limestone was seen in situ. I have not preserved any record of the exact position of these angular fragments with regard to the valleys behind, but I have little doubt that they will be found to be of glacial origin, such being certainly the case in many other similar instances. The limestone was very compact, of a blue or grey colour, and many of the fragments were almost full of coralline remains. I collected many fossiliferous specimens, which were afterwards despatched from Hanle to Simla by a messenger, on whom we thought we could rely, but they never reached their destination[10].