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 may have been effective within historic times in changing the climate and the agricultural prospects of this part of Central Asia. The Oxus itself is steadily encroaching on its right banks and depositing detritus on the left.

No fresh discoveries of minerals likely to be of high economic value to Afghanistan have been made of late years. Such as are known and worked at present have been worked from very ancient times, and their capacity is not likely to develop greatly under the Kabul government. The most important feature in this connexion which was noted by the geologist of the Russo-Afghan Commission is the existence of vast coal beds in northern Afghanistan. In 1903 some coal mines were discovered in the Jagdalak districts.

There are no glaciers now to be found in Afghan Turkestan; but evidences of their recent existence are abundant. The great boulder bed terraces in some of the valleys of the northern slopes of the Ferozkhoi plateau are probably of glacial origin. In the mountains west of Kabul glaciers have retired, leaving the moraines perfectly undisturbed. They are probably contemporary with the older alluvia.

The oldest rocks which have yet been identified in Afghanistan occur along the axis of the main watershed, and have been referred to the Carboniferous. At Robat-i-Pai near Herat, for example, there is a dark Productus limestone which seems to be identical with the Productus limestone of the Central Himalayas. These beds are conformably succeeded, along the Central Asian watershed, by a continuous series of strata which apparently represent the Permian, Trias and Jurassic of Europe. They consist of marine beds alternating with freshwater and littoral deposits, together with plant beds and coal-seams of considerable thickness. The lowest beds of this series, which from their position may belong either to the Permian or to the upper part of the Carboniferous, have yielded no recognizable fossils; but they include a conglomerate which closely resembles the boulder bed near the base of the Talchir series in India. The Upper Trias has been definitely identified by the occurrence of Halobia and other fossils; while in the higher beds of the series marine forms belonging to the middle and upper Jurassic have been found.

The plant beds occur at several horizons, and among the remains which have been found in them are several forms which occur also in the Gondwana beds of India. There can be no doubt that the series as a whole is the equivalent of the Gondwana system, and when the country has been more closely examined the association of marine fossils with Gondwana plants will be of the greatest value in determining the precise homotaxis of the Indian deposits.

The Jurassic beds are followed, generally with perfect conformity, by the Cretaceous, which covers a large part of Afghan Turkestan and probably forms the greater part of the ranges which run south and south-west from the principal watershed. The lowest beds consist of red grits which contain Neocomian fossils, while the middle and upper Cretaceous consist chiefly of limestone and chalk. The entire system may be represented in the west, but in the Herat province and in Afghan Turkestan the middle Cretaceous seems to be absent, and it is probable that, as in other regions, the upper Cretaceous covers a much wider area than the lower beds. Tertiary and recent deposits are widely spread, filling most of the valleys and covering the plains of the Helmund. Eocene beds have not yet been proved to exist; but this is probably owing to the imperfect knowledge of the country, for the formation is known in Persia, Baluchistan and the Suliman Hills. The lower part of the Miocene is marine in Herat and Afghan Turkestan; but the upper Miocene is usually of freshwater or estuarine origin. In Afghanistan, as in other regions near the great Eurasian system of folds, the Miocene includes extensive deposits of gypsum and salt. It was during this period that the forces which finally raised the country above the level of the sea began to take effect. The Pliocene consists entirely of freshwater and terrestrial deposits, which were probably laid down at the foot of the rising hills and on the floors of the intervening valleys. As the elevation continued, they were sometimes involved in the folding to which the mountains owe their origin. During this period the gradual desiccation of the country continued, and wind-blown deposits, such as the loess, began to make their appearance.

Although volcanic cones are known both in Persia and in Baluchistan, none have yet been described in Afghanistan itself. There is, however, ample evidence that at several distinct geological periods the region has been the seat of great volcanic activity. According to C. L. Griesbach, basic volcanic rocks are interbedded with the lowest part of the plant-bearing series, and enormous outbursts took place during the Neocomian period. But the most important igneous masses are the great intrusions of syenitic granite and of basic rock which penetrate the Cretaceous beds. These are probably of Eocene or of late Cretaceous age.

Omitting the group of northern routes to India from Central Asia, which pass between Kashmir and Afghanistan through the defiles of Chitral and of the Indus (see ), the highways of Afghanistan may be classed under two heads; (1) Foreign trade routes, and (2) Internal communications.

(1) Of the many routes which cross the frontiers of Afghanistan the most important commercially are those which connect the Oxus regions and the Central Asian khanates with Kabul, and those which lead from Kabul, Ghazni and Kandahar to the plains of India.

Kabul is linked with Afghan Turkestan and Badakshan by three main lines of communication across the Koh-i-Baba and the Hindu Kush. One of these routes follows the Balkh river to its head from Tashkurghan, and then, preserving a high general level of 8000 to 9000 ft., it passes over the water-divides separating the upper tributaries of the Kunduz river, and drops into the valley formed by another tributary at Bamian. From Bamian it passes over the central mountain chain to Kabul either by the well-known passes of Irak (marking the water-divide of the Koh-i-Baba) and of Unai (marking the summit of the Sanglakh, a branch of the Hindu Kush), or else, turning eastwards, it crosses into the Ghorband valley by the Shibar, a pass which is considerably lower than the Irak and is very seldom snowbound. From the foot of the Unai pass it follows the Kabul river, and from the foot of the Shibar it follows the circuitous route which is offered by the drainage of the Ghorband valley to Charikar, and thence southwards to Kabul. The main points on this route are Haibak, Bajgah and Bamian. It is full of awkward grades and minor passes, but it does not maintain a high level generally, no pass (if the Shibar route be adopted) much exceeding 10,000 ft. That this has for centuries been regarded as the main route northward from Kabul, the Buddhist relics of Bamian and Haibak bear silent witness; but it may be doubted whether Abdur Rahman’s talent for roadmaking has not opened out better alternative lines. One of his roads connects Haibak with the Ghorband valley by the Chahardar pass across the Hindu Kush. The pass is high (nearly 14,000 ft.), but the road is excellently well laid out, and the route, Which, south of Haibak, traverses a corner of the Ghori and Baghlan districts of Badakshan, is more direct. A third route also passes through Badakshan, and connects Kunduz with Charikar by the Khawàk pass and Panjshir river. The latter joins the Ghorband close to Charikar. The Khawàk (11,600 ft.) is not a high pass; the grades are easy and the snowfall usually light. This high road is stated (on Afghan authority) to be kept open for khafila traffic all the year round by the employment of forced labour for clearing snow. It is a recently developed route and one of great importance to Kabul, both strategically and commercially.

Routes that pass through the mountain barriers of the frontier between Peshawar and the Gomaloccur at intervals along the western border, and in the northern section of the Indian frontier they are all well marked. The Khyber, Kurram and Tochi are the best known, inasmuch as all these lines of advance into Afghanistan are held by British troops or Indian levies. But the Bara valley route into the heart of the Afridi Tirah is not to be altogether overlooked, although it is not a trade route of any importance. Between Kabul and Jalalabad there are two roads, one by the Lataband pass, and the other and more difficult by the Khurd-Kabul and Jagdalak passes, the latter being the scene of the massacre of a British brigade in 1842. Between Jalalabad and Peshawar is the (q.v.). The Khyber was not in ancient times the main route of advance from Kabul to Peshawar. From Kabul the old route followed the Kabul river through the valley of Laghman (or Lamghan, as the Afghans call it) over a gentle water-parting into the Kunar valley, leaving Ningrahar and Jalalabad to the south. From the Kunar it crossed into Bajour by one of several open and comparatively easy passes, and from Bajour descended into India either by the Malakand or some other contiguous frontier gateway to the plains of Peshawar.

The Kurram route involves the Peiwar and Shutargardan passes (8600 and 10,800 ft. respectively) across the southern extensions of the Safed Koh range, and has never been a great trade route, however suitable as an alternative military line of advance.

Trade does not extend largely between Afghanistan and India by the Tochi route, being locally confined to the valley and the districts at its head, yet this is the shortest and most direct route between Ghazni and the frontier, and in the palmy days of Ghazni raiding was the road by which the great robber Mahmud occasionally descended on to the Indus plains. Traces of his raiding and roadmaking are still visible, but it is certain that he made use of the more direct route to Peshawar far more frequently than he did of the Tochi. The exact nature of the connexion between the head of the Tochi and the Ghazni plain is still unknown to us.

The Gomal is the great central trade route between Afghanistan and India; and the position, which is held by a tribal post at Wana, will do much to ensure its continued popularity. The Gomal involves no passes of any great difficulty, although it is impossible to follow the actual course of the river on account of the narrow defiles which have been cut through the recent conglomerate beds which flank the plains of the Indus. It has been carefully surveyed for a possible railway alignment; and an excellent road now connects