Western Himalaya and Tibet Part 30

[Sidenote: Pa.s.sES ACROSS KOUENLUN.]

I am not aware of more than four places in which pa.s.ses exist across the Kouenlun. The most westerly of these, called in Balti the pa.s.s of the Muztagh, lies at the source of the right branch of the Shigar river, a stream which joins the Indus opposite the town of Iskardo.

The road over this pa.s.s to Yarkand was formerly frequented by merchants, but has for many years been disused, the reason a.s.signed being the danger of plunder by the hordes of robbers beyond. As described to me by persons who had crossed it, the snow is reached after ten days' journey from Iskardo, and continues during three marches. It is said to be quite impracticable for horses, from which it may, I think, be inferred that there are numerous glaciers.

The second pa.s.s is that marked in Vigne's map as the Alibransa pa.s.s, at the head of a considerable tributary which joins the Shayuk river opposite Khapalu. The enormous glacier over which this road runs, by which, in conjunction with the lateness of the season, Mr. Vigne's attempts to cross the pa.s.s were frustrated, has been well described by that traveller[33]. I did not, while in Tibet, meet with any one who had crossed it, and I was a.s.sured by the inhabitants of Nubra that they were not acquainted with any road from the upper part of their valley, either towards Khapalu or towards Yarkand.

The third pa.s.s, and the only one now frequented, is that of the Karakoram, an extremely easy though very elevated one. The most easterly pa.s.s of which I find any notice occurs on the road between Ruduk and Khoten; it is mentioned by Moorcroft[34], but without any account of the nature of the road, or the elevation of the mountains.

To the westward of Karakoram, the direction of the Kouenlun is seemingly as nearly as possible parallel to the Indus, but to the east of that pa.s.s nothing certain is known regarding it. In Humboldt's map it is laid down as running nearly from west to east, on the authority of Chinese geographical works. Its course is unquestionably to the north of the Pangong lake, but till it has been explored by European travellers its direction must, I think, be regarded as involved in much doubt. Another lofty range, however, unquestionably runs parallel to the Indus from south-east to north-west. This range, which is continuous with that by which the Indus and Shayuk rivers are separated, terminates (or more properly originates) in the still almost unknown ma.s.s of mountains which lies to the north of lake Manasarawar. Between this chain and the Kouenlun is situated a tract of country of unknown extent, which seems to be made up of a number of isolated lake-basins quite unconnected, not only with one another, but with the general drainage of the country by which they are surrounded.

[Sidenote: PANGONG LAKE.]

If we except the basin of the Pangong lake, into which Moorcroft and Trebeck descended after crossing the range of mountains parallel to the Indus, every part of this country must be viewed as a _terra incognita_. It cannot, I think, be doubted, from the description of the Pangong lake given by Moorcroft and Trebeck, that the basin in which it rests had originally an outlet at its north-west extremity, discharging itself along the valley of Tanktse into the Shayuk. The country to the eastward is so totally unknown, that it is impossible to conjecture whether the little lake-basins of which it is said to consist, discharge themselves towards the Pangong lake, or southward into the Indus.

[Sidenote: BOUNDARIES OF TIBET.]

Western Tibet, then, is a highly mountainous country, lying on both sides of the river Indus, with its longer axis directed like that river from south-east to north-west. It is bounded on the north-east by the Kouenlun chain of mountains, by which it is separated from the basin of Yarkand. On the south-east its boundary is formed by the ridge which separates the waters of the Indus from those of the Sanpu.

To the north-west and south-west its boundaries are somewhat arbitrary, unless the political division of the country be had recourse to, which, depending on accidental circ.u.mstances entirely unconnected with physical geography or natural productions, is so liable to change, that its adoption would be extremely inconvenient.

The best mode of drawing a line of separation between India and Tibet, in those parts where mountain chains are not available for the purpose, appears to consist in regarding the latter to commence only at the point where the aridity of the climate is too great to support forests of trees, or any coniferous tree except juniper.

As limited by these boundaries, West Tibet includes the whole of the valley of the Indus and its tributaries, down to about 6000 feet above the level of the sea, a considerable portion of the upper course of the Sutlej down to between 9000 and 10,000 feet, and small portions of the upper course of the Chenab, of the Ganges (Jahnavi), and of the Gogra.

[Sidenote: MOUNTAIN RANGES.]

Every part of Tibet is traversed by ranges of mountains which have their origin either in the Kouenlun on the north, or in the trans-Sutlej Himalaya on the south. These mountain ranges are generally extremely rocky and rugged, but as a general rule it may be said that they are less so in the upper part of the course of the different rivers, than in their lower parts. This rule applies not only to the Indus and to the Sutlej, but with scarcely an exception to all the tributaries of these rivers. There are no extensive open plains in any part of the country, the only level portions being in the valleys of the rivers, the width of which is usually not more than one or two miles, and very seldom exceeds five miles.

To this general description of the surface of the country I have met with no exception in those parts of Tibet which I have had an opportunity of examining. I have not, however, had an opportunity of seeing the extreme south-west portion, my knowledge of the course of the Indus not extending further up than Hanle[35].

The height of the mountain ranges which traverse West Tibet is in all parts pretty much the same, and, as a consequence, the depth of the valleys in the lower portion of the course of the Indus and of all its tributaries is very much greater than near the sources of these rivers. In the higher valleys therefore the mountains are apparently much less lofty; they are also frequently rounded and sloping, or at all events less rocky and precipitous than lower down, though to this there are many exceptions.

[Sidenote: ELEVATION OF Pa.s.sES.]

The elevation of the pa.s.ses in a mountainous region represents in general the height of the lowest part of the chain. In the mountain ranges of Tibet the average height of the ridges does not exceed from 1000 to 2000 feet above the pa.s.ses, many of which indeed are scarcely at all lower than the highest crest of the ridge in which they are situated. I believe that in estimating the princ.i.p.al ranges of mountains at 19,000 feet, and the minor ranges at from 17,000 to 18,000 feet, I approximate very closely to the truth. This estimate applies to all parts of the country, the height of the ranges being remarkably uniform; but peaks occur at intervals in every one of the princ.i.p.al mountain ranges, which considerably exceed the elevation just stated, rising very generally (so far as can be judged by the eye from known heights of 17,000 and 18,000 feet) to twenty-one or twenty-two thousand feet; some peaks appearing to exceed even this.

It is generally supposed that the great peaks of the Himalaya on the southern border of Tibet are much more lofty than the mountains of the interior of that country. I do not think, however, that the facts of the case are such as to warrant this a.s.sumption. West of the Sutlej, in which district only the mountains of Tibet may be said to be at all known, many peaks of the interior of that country are probably much more lofty than any of those near the plains of India, and if inaccessibility is to be any criterion, the chain of the Kouenlun is beyond a doubt a much more elevated ma.s.s than any part of the Western Himalaya. Of Tibet east of the Sutlej little is known, except that between Ruduk and La.s.sa no road into the interior of Asia appears to exist.

[Sidenote: CLIMATE.]

The climate of Tibet is in every part extremely arid, because it is surrounded almost entirely by ranges of mountains so elevated that the rarefied air which pa.s.ses over them can contain only a very small proportion of aqueous vapour. Along the Indus, indeed, no mountain chains are interposed to obstruct the pa.s.sage of moist air, but the lower course of that river lies entirely in a comparatively dry climate, so that the winds which blow over the plains of Sind and the lower mountains of Eastern Affghanistan cannot convey any excess of moisture to lower Tibet. In the few Tibetan valleys which, like that of the Sutlej, are traversed by rivers debouching on the plains of India in a rainy climate, the quant.i.ty of moist air which they can receive being limited to that which proceeds directly up the valley, the upward current, even when saturated with moisture at the commencement, being gradually rarefied by the increasing elevation of the river-bed, and meeting with descending currents of cold air in its course, it very early deposits its moisture, first in the form of light showers, afterwards of fog and mist, and in its further progress is just as dry as the air in the more interior parts of the country.

[Sidenote: RAIN-FALL.]

It will probably be long before lengthened registers of meteorological phenomena will be obtained from all the different stages between India and the central parts of Tibet, so as satisfactorily to establish the gradual transition of climate. Till such shall be the case, the best evidence from which to deduce the fact of the alteration of climate, is afforded by the gradual change in the vegetation of the country as one advances towards the interior. Direct observation will probably at some future period fix the point in the outer Himalaya, at which the quant.i.ty of rain--always greater, _caeteris paribus_, among mountains than in level countries--is a maximum. I believe that in the Western Himalaya the greatest quant.i.ty of rain will be found to fall on mountains elevated from seven to nine thousand feet. Ranges of mountains which attain an elevation of from ten to eleven thousand feet have already (in the Western Himalaya) a very sensible effect in diminishing the quant.i.ty of moisture, as indicated by the vegetation; and when the mountain chains became sufficiently elevated to be capped by perpetual snow, they condense a very great proportion of the moisture of the air-currents which pa.s.s over them.

To a traveller who penetrates directly to the Tibetan interior from the plains of India, the change of climate is perceptible to the senses; most markedly so of course if his journey occurs during the Indian rainy season. Even during the rains, however, the irregularities which everywhere occur in the fall of rain prevent the gradations of climate from being ascertained during a journey with the precision which a lengthened series of observations would permit; but the phenomena of vegetable life, which are dependent on the average seasons, are not affected by accidental irregularities, and therefore form an unerring guide.

[Sidenote: CLOUDS.]

Though the climate of the whole of Western Tibet may, in general, be characterized as extremely dry, it is by no means cloudless. The winter months in particular are often very cloudy, and a good deal of snow falls. During the summer the sky is either bright and clear, or overcast with very light clouds. These clouds, usually cirrhi, are in general elevated and extremely thin. The cirrhus, when it remains for any length of time, changes or increases into a uniform hazy stratum, which covers the whole sky; more rarely, and perhaps only by an optical deception, it is seen under the form of stratus. c.u.muli are very uncommon. After several dull days the clouds generally acc.u.mulate, descend lower in the atmosphere, and rest on the mountain; as a few drops of rain fall in the valleys, the clouds disappear, and the highest peaks are seen to have received a slight sprinkling of snow, which is soon melted by the rays of the sun. It is only very rarely that the quant.i.ty of rain exceeds a few drops, or merits the appellation of a shower. The few occasions on which I have observed any fall of rain, at all deserving of being called by that name, have mostly been in early spring or in the latter part of autumn.

[Sidenote: TEMPERATURE.]

When the sky is clear, the sun, in all parts of Tibet, even at great elevations, but especially in the valleys at and below ten and eleven thousand feet, is extremely powerful. The shade temperature depends, of course, in a great measure on the elevation above the level of the sea, but also on the situation, exposure, and many other accidental circ.u.mstances. In the lower part of the Indus valley, at elevations of seven and eight thousand feet, it is said to be frequently very high[36], the clear dry atmosphere allowing the full influence of the sun to be exerted on the bare, often black rocks. Even as far up as 11,000 feet, in narrow valleys, the heat is often great in the middle of the day, but the more open plains are generally very temperate in the shade, and the nights and mornings are always cool.

On the tops of the lower pa.s.ses, and in the alpine valleys, the temperature of the nights and mornings is, in clear weather, very much depressed by radiation, so that the mornings, except when the sky is overcast, are intensely frosty, at elevations of 15,000 and 16,000 feet, or far below the level of perpetual snow. This is the case even in the month of August, which is the hottest of the year. The shade temperature at these high elevations rarely rises very high, even when the heat of the sun is oppressive, as it is moderated by the action of the violent winds which so generally prevail.

The periods of cloudy sky, which now and then alternate with the bright sunshine, which is the prevailing weather, are in the alpine regions extremely cold. The stratum of cloud, at first high in the atmosphere, gradually lowers itself, and the traveller is enveloped in a frozen mist, followed most commonly during the night by a fall of snow. The quant.i.ty of snow which falls is very small, seldom, so far as I have seen, more than an inch or two in depth, and it speedily disappears as soon as the clouds have been dissipated and the sky resumes its usual serenity.

[Sidenote: WINDS.]

The whole of Western Tibet is subject to extremely violent winds, the course and direction of which could only be satisfactorily studied by a resident. From the great depth of the valleys, the wind in general follows their course, blowing at one time up them, at other times down. In unsettled weather the direction is extremely variable, often changing repeatedly in the course of the day, but in clear settled weather the direction of the wind is, during the day at least, more frequently up the valleys than in the contrary direction. I have not observed any constancy in the course of the wind on the pa.s.ses, on which it would be princ.i.p.ally important to be acquainted with it, but it probably varies in direction according to the period of the day, so that a traveller, whose time does not permit him to delay to register the changes as they occur, is not likely to be able to discover any general law.

The Tibetan wind, in the ordinary state of the atmosphere, commences after the sun has nearly attained the meridian, the mornings being in general quite calm. It increases in violence during the afternoon, sometimes till after sunset, ceasing to blow after dark, or at all events before midnight. This wind seems to be pretty constant over the whole country, from the upper Sutlej as far west as Rondu; and as a very similar wind blows in the valleys of Affghanistan, which have an identical summer climate in respect of moisture, it must, I presume, be caused by the influence of the sun, in heating the barren rocky plains and hills.

During periods of cloud, and throughout the winter, the wind is much less regular in its direction, as well as in the periods during which it blows. It frequently changes its direction very abruptly. About the equinoxes, or at the commencement and end of winter, at which times there seems to be generally a good deal of unsettled weather, it blows for some days with extreme violence. In March, 1848, at Iskardo, for several nights the wind almost amounted to a hurricane; its direction was from the south, or directly across the mountains. This was very commonly the case at Iskardo, in unsettled weather, during the winter, but never when the days were bright and cloudless.

[Sidenote: SNOW-FALL.]

The amount of snow-fall varies much, diminishing as we advance into the interior of the country, but being always much greater on the mountains than in the valleys at their feet. In the outer Himalaya, the amount at equal distances from the plains diminishes as we advance westward, but in the Kouenlun, where the source of moisture lies to the westward, the snow-fall diminishes rapidly from west to east. The same is the case in the valley of the Indus, where the amount of winter's snow, except in the most westerly parts, is quite insignificant.

It is probably owing to the absence of c.u.mular clouds, and to the general uniform expansion of the condensed vapours over the whole sky, that the outward manifestations of electricity--thunderstorms--are of very rare occurrence in Tibet. I find only one instance of a thunderstorm recorded as having been observed while I was in a Tibetan climate. This was at Le, in September, 1848, at which time there was a good deal of cloudy weather for several days. From the extreme dryness of the air, electricity is evolved with great facility by friction: all articles of woollen clothing, blankets, and even the hair, emit sparks when rubbed in the dark. I have even observed this to be the case at the elevation of 15,500 feet, in cloudy weather, when snow was falling.

[Sidenote: GLACIERS.]

In every part of the Himalaya, and of Western Tibet, wherever the mountains attain a sufficient elevation to be covered with perpetual snow, glaciers are to be found. The occurrence of glacial ice is a sufficient indication of the existence of snow of more than one year's duration, and (setting aside trifling cases of ma.s.ses of ice in deep and sunless ravines, which, indeed, are not an exception, as they have no motion,) it may be laid down as a general law, that every glacier has its origin in perpetual snow.

The converse of this proposition does not seem to be so universal. We have the high authority of Humboldt for the fact, that no glaciers occur in the Andes of tropical America, from the equator to 19 north lat.i.tude. Nor is it, I think, possible that the existence of glaciers should have escaped his notice, did they occur of such dimensions as would be indicated by the solitary and doubtful instance mentioned by M. Boussingault, to which Humboldt refers[37], which is stated to have been seen at the same elevation as the town of Quito, or more than 5500 feet below the level of perpetual snow in that region of the Andes. The cause of the non-existence of ma.s.ses of moving ice, in connection with the perpetual snow of the American tropics, must apparently be sought in the extreme uniformity of the seasons, and in the small quant.i.ty of snow which falls at any time of the year.

In every region of the earth, so far as is known to me, where the mean temperatures of summer and winter are very different, or where the climate is what is called excessive, perpetual snow produces glaciers.

These rivers of ice, as they have most appropriately been called, vary very much in size and appearance. In the lofty chains of the cis- and trans-Sutlej Himalaya, and of the Kouenlun, whose peaks rise to a very great height, and collect in winter enormous depths of snow, they are of great length. In the central parts of Tibet, which are often lower, and even in their loftiest parts are less snowy than the bounding chains, the glaciers are of inferior dimensions, often of that kind which I have called incipient, where the snow-bed is at once cut off abruptly in an ice cliff, which can hardly be said to be in motion, or rather whose motion must be almost entirely from above downwards.

The general appearance of an Indian glacier seems in every respect to accord with those of Switzerland and of other parts of the temperate zone. It is only of late years, indeed, that they have been generally recognized in the Himalaya; but it must not be forgotten that it is only recently that the researches of modern investigators, and in particular the delightful work of Forbes, have familiarized the untravelled world with their appearance, and more especially with the fact and cause of their motion. It has also, singularly enough, long been the custom to look upon the Himalaya as a tropical range of mountains, in which it was, as a matter of course, regarded as impossible that glaciers could exist[38].

The upper end or origin of a glacier seems commonly to be in an enormous snow-bed, occupying the whole s.p.a.ce included by an amphitheatre of snowy peaks. The snow-slips and acc.u.mulations by which the snow-bed is added to during winter, must to a great extent remain concealed from human eyes; and in summer, when these icy fields are accessible, they are generally, I believe I may say always, covered by a thick layer of snow, which a.s.sists at the same time that it conceals the process by which the snow is converted into ice.

I have never measured the dimensions of any of the great glaciers of the Himalaya, nor is it easy to ascertain the length of any of them even approximately, as they are seldom traversed by roads, and are usually bent so that only a small part of their course can be seen.

Many of them must considerably exceed ten miles in length; I have seen several which were more than half a mile broad; and the depth of the icy ma.s.s frequently amounts to hundreds of feet.

The appearance of the surface of a glacier seems to depend almost entirely on the inclination of its bed. Where the slope is gentle the surface is nearly uniformly smooth, or at most only slightly fissured.

I have not had occasion to observe any fissures of more than a foot or two in width, so that, though often very deep, they are crossed without difficulty. In describing the icy surface as smooth, it is necessary to mention that such is only the case in the upper part of the glacier, where the moraines are small or only lateral. Whenever the surface supports rocky fragments in great quant.i.ty, it is extremely unequal till such time as the whole superficies becomes covered with stones, when the melting being uniform, the surface again becomes tolerably even.

On steeply inclined planes the glacier is traversed in every direction by enormous fissures, between which the surface is very irregular, rising into sharp icy pinnacles of the most fantastic shape and appearance. More than once I have seen extremely steeply sloping glaciers, which were terminated abruptly by a lofty precipice, at the bottom of which huge piles of boulders and occasional icy fragments sufficiently indicated the forward motion of the ice; at other times, the slope of the valley in which the glacier lies again becoming gentle, the ice ceases to be fissured and rugged, and is capable of being walked on without difficulty.

Moraines, which, on the larger glaciers and among mountains of easily decaying rocks, are of astonishing dimensions, form the margins of each glacier, and also occur longitudinally on different parts of their surface, increasing in number as the glacier advances, till at last the different series whose origin can long be traced to the different ramifications of the glacier, become blended into one. The nature, origin, and aspect of the moraines, the mode of melting of the ice beneath them, and the isolated pinnacles of ice which support large solitary boulders, agree so entirely with descriptions of glaciers in other parts of the world, that it is unnecessary to dwell upon them. The large glaciers are often a good deal lower in their central parts than where they are covered by a bulky moraine; and a curious ravine-like hollow, between the moraine and the bare ice, which makes the former appear as if entirely disconnected from the glacier, is of very common occurrence. There is, however, also very often an ancient moraine, not now resting on ice, which runs parallel to the glacier, and seems to indicate its former greater extent.

[Sidenote: FORMER GREATER EXTENSION OF GLACIERS.]

In every part of the Tibetan mountains, and in very many parts of the Indian Himalaya, I have thought that I could recognize unmistakeable proofs of all the valleys having been formerly occupied by glaciers at much lower levels than at present. At first sight it seems rather improbable, that in sub-tropical lat.i.tudes the present extension of perpetual snow should at any former period have been exceeded; but it would not be difficult to show that the mean temperature, and particularly the mean summer temperature, is very much higher in the Western Himalaya and Tibet than it might fairly be expected to be in such a lat.i.tude. In fact, in the more humid climate of Eastern Bengal, though at least four degrees nearer to the equator, the mean summer temperature at equal elevations in the mountains is probably considerably lower than in the mountains of North-west India, and the snow-level is certainly lower. It is fair, therefore, to conclude, looking back to a period when the sea washed the base of the Himalaya in the upper part of the Punjab, that at that period a very different state of atmospheric circ.u.mstances prevailed from that which we find at the present time.