« السابقةمتابعة »
the older formations present such a similarity to each other, as to render it impossible to point out any specific distinction. Thus Humboldt has made this remark, in regard to the rocks occurring in the Andes,* discovering no difference between them and the European of the same comparative ages. The same remark has been madet and pointed out to us by Professor Jameson, which is amply verified by the extensive geological collection brought together from all quarters of the world, consisting of upwards of thirty thousand specimens deposited in the Edinburgh Royal Museum; nor have we met with any rocks among the Himmalehs, differing from those we have seen in Europe.
That the newer formations exhibit in different countries, different characters, we were entitled, a priori, to infer. Thus the American tertiary deposits, as has been proved by the researches of Rogers, &c., are quite different from the European; but it has been shewn from the first time these deposits were described, that they, in their distribution, were circumscribed, hence the name given to them by their discoverer Wemer, of local deposits.+
In extent, the Himmalehs are calculated to be upwards of 2,000 miles, running in a north-east and south-west direction. In such a vast extent of mountainous country, we have the individual mountains assuming all variety of forms, varying according to the nature of the rocks; thus we have peak-shaped, conical, dome, roundbacked, saddle, table, &c. To pay attention to the form of mountains in connexion with the rocks which compose them, is of the greatest consequence, it being a well known fact that the shape varies with the rock, and an experienced geologist can, with a good telescope, distinguish, and that too with great accuracy, what a distant country may be composed of.
From the different countries through which this mighty chain runs, it has received various names. Thus its continuation to the west has been called Hindoo Cosh, which by Humboldt is considered as the continuation of the Kuen line; of the Macedonians, it was the Emodus; and the Imaus of Pliny; it probably also, in those days, was called Himmalehs, as the Greek title was borrowed from the Sanscrit.§ In its prolongation to the eastward, according to Colonel Kirkpatrick,
* Humboldt on the superposition of rocks.
† Appendices to Capt. Ross and Parry's Voyages, and Cabinet Library, vols. Polar Regions, Africa, &c.
Cuvier's Theory of the Earth. By Professor Jameson, Notes to 5th edition. § Journ. Geograph. Soc. vol. IV. p. 63.
it is called Humla to the north of Zumila, and beyond the Arun, according to Hamilton's map, appended to the History of the Goorka war, the Harpala mountains. Klaproth and Abel Remusat have collected from Chinese writings, the continuation of the chain in the snow-clad peaks to the west of Young-Schan. These turn abruptly to the north-west on the confines of Hon-Konang, advancing ultimately, according to Von Humboldt (who seeks in description, geography for the evidence of the elevation of mountain chains on longitudinal fissures) to the sea, and terminating in the island of Formosa.* We shall afterwards take an opportunity of inquiring into those views of Humboldt, and point out the observations upon which they are founded, being interesting not only to the geologist, but also to the geographer. To make a geological survey of such a vast extent of country, even if permission were granted to traverse many of those tracts inhabited by barbarous, half civilized, and jealous tribes, is a vast undertaking, and would be the labour of many years. The researches of Humboldt, Ehrenberg, &c. have laid open to us a great part of western Asia; of the countries between it and India proper, we possess but little information, and that we owe to Burnes, Bell, Sterling, &c.; we have here therefore still a great desideratum.
For many years the Himmalehs were considered the highest mountains in the world, lately however it has been proved by an observer of well known accuracy, Mr. Pentland, that they are surpassed by some of the peaks of the Andes; of the passes, the lowest, the Tungmug, is calculated to be 13,739 feet, and the highest, north-east of Koonawur, is 20,000, which allowing the culminating points of the chain to be 28,000, would give a relation of the main height of minimum of crest to the culminating point of 1:1:6;+ Humboldt many years ago reckoned it at 1: 1:8.
In regard to valleys, it has been stated, that the direction of the principal valleys is in general at right angles, or perpendicular to the central or high mountain chain; whether this is the case in regard to the principal valleys of the Himmalehs, is a question; at present we are inclined to believe that they are not, and that they are parallel to the central chain, and thus forming those kind of valleys properly denominated longitudinal or parallel.
In groups of chains of mountains, as in the Himmalehs, it has generally been shewn, that there is a central or high mountain chain,
* Journ. Geogaph. Soc. IV. p. 63. ↑ Journ. Geograph. Soc. p. 63.
from which shoot at right angles smaller chains, named principal chains, and that between these the principal valleys occur; subordinate to these, we have other mountain chains, running at right angles, or perpendicular to the principal, and termed secondary chains, and the valleys between these, secondary valleys. That however does not appear to be the grouping of the mountain chains among the Himmalehs. Here we have the principal, secondary, tertiary, &c. chains running parallel, as already mentioned, in regard to the valleys to the central or high mountain chain;* as examples of valleys running parallel to the central chain, we may give the Dehra Dhoon, and the Punjore Dhoon. The appearance presented by many of the small lateral valleys is remarkable, occupying the upper two-thirds, or half of the mountain, and forming that kind of valley, which has been denominated "Coorie "+ In the neighbourhood of Bunnassur, there are many fine illustrations. Another very remarkable appearance is presented by the valleys first pointed out by Bourquet, as occurring among the valleys of the Alps, viz. salient and re-entrant angles. In regard to this appearance in the Perynus, Raymond says, which is quite applicable to many of the valleys between Bhar and Simla, "that the angles so perfectly correspond, that if the force which separated them were to act in a contrary direction, and bring their sides together again, they would unite so exactly that even the fissures could not be perceived."
On ascending the mountains towards Simla, and in fact in every direction, an appearance is presented, which strikes much the attention of the traveller on his first visit, we allude to the terraces on the acclivities, bases, and summits of mountains, resembling much the parallel roads of Argyleshire, so ably described by Sir T. Dick Lauder,‡ they however, like the Scotch, are not parallel to each other on the opposite side of the valleys, and moreover they occur every where,
* Physical Geography is at present but in its infancy, the description of the form and grouping of mountains is but imperfectly understood, and much neglected. In books of travels, the vague descriptions given in general, are quite beyond comprehension. In this country scarcely any attention has been paid to the subject, though presenting probably the first field in the world for observation. We shall afterwards inquire into the age of mountain ranges, based upon their parallelism, a supposition first advanced and ably defended by the celebrated Beaumont, when we have examined more of the Himmalehs, which will allow us to compare this mighty range with those on the European, American continents.
† Imagine an oblique truncation, partly hollow in the upper two-thirds, or half of a mountain, and we have the appearance represented.
Sir T. Dick Lauder's explanation being generally so well known, it is useless for us to notice it here. See Trans. of the Royal Soc. Edinburgh.
throughout the mountains. That they have been produced artificially by man, is evident from these two facts, it is also the method adopted in cultivating the mountains at the present day; we never however, (at least very seldom) see cultivation carried to the summit of mountains, which appears generally to have been the case in former times, shewing that husbandry must have been carried to a much greater extent by the former inhabitants of the hills. There is ancther fact pointed out to us by Mr. G. Clerk, which goes far, if other evidence was wanted, to prove, that the terraces generally were produced by artificial means, viz. that in those places where they are well marked, we never see old trees, and again in those places where there is not a vestige of them, we meet with trees of great dimensions, pointing out that in all probability these tracts were unworthy of cultivation, and that therefore any thing was allowed to grow; in general where the latter occur the acclivity is steep.*
In regard to the different parts of a mountain. The foot among the Himmalehs is generally found, owing to the steepness of the acclivity to occupy but a very small proportion; the acclivity is always the most extensive part, its angle varying from a few degrees, to the mural. The summit in general is very steep, and frequently truncated, if we may be allowed to use the expression. Soil. The superincumbent soil, from the nature of the rocks, is in many places very good, presenting a rich vegetation. It is of two kinds, transported and untransported; of the former, we have five examples in the valley ascending from Pinjore to Bunnassur, being in many places upwards of 150 feet in thickness, and with boulders, many of an enormous size, of rocks quite different from those we meet with in the neighbourhood. In crossing Hurreepore bridge, and ascending towards Subbathoo, there is another fine example. That these are transported soils, is evident, not only from the nature of the boulders which occur, embedded; but also from their form being always rounded, shewing that they must have been brought from some distance, and subjected to considerable attrition. Into the age of these deposits we shall afterward inquire, our examination as yet being of too trivial a nature to allow us to speak definitely. It has been
* Dr. Griffith in his account of the mission to Boutan, states, that he found many of the "lower mountains curiously marked with transverse ridges." These he further adds, "have much of the appearance of ancient terrace cultivation, but on inquiry, was assured that such was not their origin." He does not give any explanation as to the manner in which they were produced; probably, however, they may have been found in the same manner as the Scotch parallel roads. For Dr. G's. remarks, see Journal of the Asiatic Society, New Series.
stated to us, that in the first locality, bones of fossil animals have been found, either imbedded, or in the neighbourhood. If the first statement should turn out to be correct, of which however he is doubtful, it may probably be the means of allowing us to draw conclusions in regard to the age of these deposits generally throughout the Himmalehs. To these transported soils we therefore beg to direct the attention of observers; of the latter, or untransported soil, we have of course abundance of examples. In many places it is of great thickness, as has been shewn by some sections lately made at Simla on the road from Subbathoo to the village of Draw, it also occurs in many places, of great thickness. This kind of soil is formed by the decomposition of the subjacent rock, or rocks and vegetable matter, and contains in general imbedded angular fragments of the rocks which occur in the neighbourhood. In regard to boulders, it may be stated, that there are two kinds, which may be denominated natural and artificial, the former produced by decomposition, the latter by attrition. To account for boulders in many cases on the summit of mountains, many erroneous statements have been made, and absurd theories proposed, which would have been avoided if the author had paid attention to this, and examined the mineralogical characters of the boulders, and of the rocks in situ; for instead of finding that the boulders had been brought from a distance, it would have been discovered, that they were in their original position. In trap and granitic districts, these natural boulders are frequently met with; in the former, caused by the oxydation of the iron, which enters more or less into the composition of all traps, and frequently in its least oxydized state, and thus tends to combine with more oxygen; in the latter, by the decomposition of the alkali of the felspar (generally potassa) a substance frequently found in the felspar of granites;* the earth which remains is the celebrated Porcelain earth. To find trap on the ground scale exhibiting the columnar structure, and each of the columns composed of a series of balls, is not unfrequent. It is in these districts we meet with so frequently natural boulders of trap; if we examine minutely into the structure, we shall find that the concretions are
* Analysis of rocks is a subject, which has as yet engaged but little attention; we are glad to see that one chemist in this country (Professor O'Shaughnessy) is paying some attention to the subject; it will amply repay his trouble, opening up a wide field of discovery, and at the same time giving to geologists the means of validating or refuting many of the theories, in regard to the formation of rocks which have been advanced. We hope therefore the Professor, who in his splendid laboratory has every thing at his command, will take the opportunity of conducting operations upon a more extensive scale, and at the same time give quantitive analysis.