ÆäÀÌÁö À̹ÌÁö
PDF
ePub

could have been uplifted from under the sea to an elevation of 15,000 feet," without losing its horizontality, whilst not only the beds on which the "true sea-bottom" rested, but the probable contemporaneous beds of the Sewaliks (according to Captain Strachey's hypothesis only,) are dipping N. E. at a high-angle. Captain H. Strachey describes the same bed, where it extends into Ladak, as old alluvium, and mentions its containing fossil bones of extinct mammals. Captain Godwin Austen calls these beds, in Ladak, Rodok and Skardo, a fluviatile deposit. The bed is not limited to the belt of country situated between the Ser and Mer (Snowy Peak Range) chain and the Kailas chain. It is well developed in Rodok, near the Pang Chong Lake and up to the foot of the Korakoram chain, and it is very probable that the great Desert of Aksai Chin is a similar bed. I have said, in another place, that I believe these horizontal beds to be identical to the Ragzaier or elevated plateaux of the Afghan mountains. How were they formed?

In order to answer this question, let us consider what was the physical topography of the Himalayas soon after their final upheaval. There was not much difference in the configuration of the great ocean between the tropics; if we are to believe the geologists who have studied the Andes, these mountains had not yet appeared; the great plains of Africa, Arabia, Persia and India, were still under water; the mountains of the Indian peninsula may have appeared (and did probably appear at the time of the Himalaya's last upheaval) but were separated from the Himalaya by a considerable sheet of water; the great inland sea now represented by the desert of Gobi was not yet dry,-in short, there was little cause to diminish the humidity of the winds which blew from the south, and there was nothing to change their old direction. But the Himalayan and Afghan mountains were very different from what they had been. Instead of low ranges with volcanic peaks which did not probably soar above 5,000 or 6000 feet, we have now an immense wall, some hundred miles broad and 25,000 feet high, with deep longitudinal valleys offering no exit and much embarrassed by detached rocks and debris. The humidity of the winds which produced the tremendous rains of the Miocene period was now deposited as snow. Huge glaciers appeared and filled the longitudinal valleys, and the rivers which ran from them

began to deposit a sediment which, in time, formed the great flat plateau of Thibet, Rodok, Aksai Chin, &c. &c. Thus we see the altered physical conditions which were brought about by the difference of elevation of the Himalaya, before and after its final upheaval. Before the upheaval, the humidity was collected as rain, and the mountain debris was washed to the coast by boisterous torrents; but after the upheaval, the humidity was collected as snow, and the mountain debris was quietly collected in the great valleys, under the cover of glaciers.*

All the while, a different action was going on in the outer or low Sub-Himalayan ranges. There the humidity continued to fall as rain and great denudation was the result. The same process of land gaining over the sea, which I have described at the Miocene epoch, began to form the plains of India; this process is still in operation now-a-days, but necessarily its power diminishes in intensity as the sea-coast becomes more distant from the hills and the course of rivers becomes longer. It is the process which is now anxiously watched by the pilots of the Hooghly, and which no engineering skill can avert the sandbanks advance in the sea, the river-bed fills up, more dry land appears and what was yesterday a dangerous shallow out at sea, to-day is the shore of the delta, and to-morrow will be far inland.

As the plains of India extended, the rain-fall of the Himalaya diminished. Even if we suppose the humidity of the winds to have been the same as before, we must deduct from the Himalayan rain-fall the amount of rain which fell in the plains. But we know that the humidity of the rains had also become less; the Andes had surged up and the South-American continent had appeared; the plains of Africa, Arabia, Persia and Central Asia were gradually appearing above the waters, and instead of the trade winds, the monsoons were establishing themselves. There was therefore a great diminution in the snow-fall on the Himalayas, and the glaciers began to decrease and to expose a great deal of the plateau on which they had gradually raised themselves. It is easy to understand how this decrease of snow-fall

The filling up of the great parallel valleys of the Himalayas by mud and boulders, under the cover of the glaciers, is analogous to the filling up of depressions of the surface by the glacial drift in some parts of Europe. The glaciers of the Himalaya, soon after the great upheaval, were too huge and too general to have had a ploughing and scouring action on the valleys.

must have been very gradual, if we keep in mind what brought on that decrease; and as the glaciers retreated, animals advanced and soon populated the high plateau of the Himalaya. These animals have left their remains interred in the clayey grits of these elevated lands. It may appear strange that elephants once lived at such a great height, and in a climate so cold, but the osseous remains found in the elevated plateau of Mexico belong to true elephants of extinct species, and the Siberian mammoth which was covered by a warm fur, lived on the leaves of conifers and roamed over the ice-drift. There is therefore no doubt that these animals had a great plasticity of organism, and could adapt themselves to very extreme climates.

The mammals discovered in the plateau of Thibet and Ladak, all belong to extinct species. On the other hand, all the shells which I have been able to collect in the old alluvium found near the foot of the Sub-Himalaya belong to living species, and it is therefore most probable that the older alluvium of the plains of India, and the high plateau of the Himalayas belong to the post-pliocene epoch.

From the above considerations, and the present state of our knowledge, it appears that the Afghan and Himalayan mountains suffered their last upheaval during the pliocene period.

99. The description of the deposition of beds subsequently to the great upheaval has been given incidentally in the preceding paragraph; the glaciers began to melt, great lakes were formed in several localities. The Kashmir valley is a good example, Rukshu is another, and so is Abbottabad valley. These lakes at first fed large rivers, and both lakes and rivers had a considerable power in carrying mud, sand and boulders, and thus raising their beds by several hundred feet; but as the waterfall diminished, the lakes and rivers diminished also, and the rivers soon began to cut for themselves deep ravine-like beds in the middle of their ancient bottoms, leaving on each side a great river-terrace.

Before the rivers had lost their great volume, however, and while they filled the whole of their original beds, they floated icebergs of sufficient dimensions to carry blocks of stone of great size. The SaltRange for a time intercepted the free passage of the waters towards the south and a shallow lake filled the whole country between it and the

* Cosmos, Otte's translation, Vol. I. page 280.

*

Munee Range. On this lake floated the icebergs brought down by the rivers, drifting gradually to the south, and finally grounding near the Salt-Range or averted by it. Thus we see between Jubbee and Nikkee large erratic blocks, being porphyry, resting on the top of the old alluvium; and we find similar but smaller blocks imbedded in horizontal taluses of debris which have been piled up in horizontal layers against the hills of Maree on the Indus. These blocks are not water-worn, but present either flattened or scratched surfaces; the ground all over that district is covered with boulders of porphyry, greenstone, felstone, &c. but these boulders are well rounded and are easily traced to disintegrated beds of Miocene conglomerate. The erratic blocks are very different in appearance, and have the striking, or somewhat odd and déplacé aspect peculiar to erratics. One of them, three miles south of the village of Thrapp, measures 6 feet 4 inches by 7 feet 4 inches and 5 feet. There are four or five smaller blocks near it, but none are rolled; they are all of the gneissoid porphyry of the Kaj-Nag. The largest presents the very singular appearance of having its greatest flat surface (not vertical) marked with a number of cup-like holes of various size, from 6 inches across to the size of a walnut, and from 1 to 2 inches deep. There are from 70 to 75 of these cups. They resemble wide rounded holes or cups, as water would make by dropping. Whether these cups are a glacial effect, or have been made by a race of men for some unknown purpose, is, what I am unable to decide. I am inclined to the first hypothesis.

[graphic][merged small]

100. The oldest indications of Man having become an inhabitant

*The damming of the water behind the Salt Range and the Chitta Range was the cause of that thick deposit of silty mud now cut by ravines, which has been the source of so much difficulty and expense in making the great Trunk Road between Jheelum and Attok. A similar damming occurred in the Huneepor valley and several other localities, but to a less degree.

of the Himalayas is, at present found in the Upper Lacustrine deposit of Kashmir (see note to para. 44). This deposit contains a very great many fragments of pottery, bones of goats, and pieces of charred wood. It is much older than the Buddhist ruins of Avantipoor, and attests the presence of man in the valley during the period which elapsed between the first and the second lake. The Buddhist ruins were not built until after the second lake had been drained. But though we may call the race of men who lived in Kashmir before the second lake historically ancient, they cannot be considered so geologically: a cowry has been found in the deposit, and this evidence of a currency indicates at once an amount of civilization and trade far removed from the state of the primitive races.

(To be continued.)

Experimental Investigations connected with the supply of water to Calcutta, Part III.

By D. Waldie, Esq.,

F. C. S. &c.

(Continued from page 8.)

[Received 1st March, 1867.]

The present communication is intended to give an account of the results obtained in prosecuting the investigations indicated by the title, the first of which have already appeared in this Journal. To some of the results given in the original paper objections were raised, which were examined in a subsequent article, entitled, " Supplementary Observations, &c.," these being founded on experiments made during the month of September last. Since that time the enquiry has been continued, with the view of more fully examining these objections, of supplying certain deficiencies, of correcting some errors, clearing up some obscurities, and generally rendering the enquiry more complete.

I propose also to endeavour to correct some misapprehensions which seem to have arisen, and indicate points of importance which do not

The cowry was discovered by Captain Godwin-Austen while we were examining these lacustrine beds together. I saw Captain Austen dig it out of the clay with his penknite.

« ÀÌÀü°è¼Ó »