網頁圖片
PDF
ePub 版

ridges of the Himalaya, which here comprise Bhután and the outlying border of Tibet, and include some of the most irreclaimable and uncivilised of Himalayan tribes. On the south the rough tableland of the Garo, Khasi and Jaintia Hills intervenes between the valley and the Cachar districts of Eastern Bengal drained by the Surma, ere the Surma joins the Brahmaputra after the latter has turned the western flank of the hills. Assam is the valley of the Brahmaputra, and it owes its wealth of agricultural resources-even its very existence—to that silt-bearing river. The Brahmaputra rises, like the Sutlej, near the sacred lake of Manasarawar. For 800 to 900 miles it flows steadily eastward through Tibet as the Tsan-pu, passing to the south of Lhasa, the Tibetan capital. Then, turning the eastern flank of the Himalaya, and receiving a few Chinese tributaries, it twists into Assam under the name of the Dihang. At this eastern bend it takes up the Dibang from the north and another stream (which is also named Brahmaputra) from the east, and finally, as the "Son of Brahma, the creator" (i.e. Brahmaputra), it proceeds to increase and fertilise the valley of Assam. Its drainage basin is 361,200 square miles, and its mean low-water discharge at Gualpara, near the head of the valley, amounts to 116,500 cubic feet per second. After receiving the Subansiri from Tibet the total flood discharge must be over 500,000 cubic feet. "The Brahmaputra rolls down the Assam Valley in a vast sheet of water, broken by numerous islands, and exhibiting the operations of alluvion and deluvion on a gigantic scale. The vast quantity of silt brought from the Himalaya is deposited in banks at the smallest obstruction, and islands form and re-form in constant succession. Broad channels break away, and rejoin the main river after wide divergences which are subjected to no control. The swamps which closely adjoin the elevated alluvial foundation of the river bed are flooded in the rainy season till the lower reaches of the valley are one vast shining sea, from which the hills slope up on either side. After 450 miles of open course the river turns the western flank of the Khasi Hills. Here it becomes the Jamúna for 180 miles of southerly flow across the flat plains of Bengal till it joins the Ganges at Goalanda. Then the deltas unite. After the Surma has joined from Cachar the united stream of the three great river systems takes the name of Meghna and rushes to the sea. Goalpara and Dibrugarh are perhaps the best known stations of the upper Assam Valley, and on the

Khasi Hills to the south stands the well-known hill sana

torium of Shillong.

Lastly there remains Burma to be described, Burma the land of picturesque rivers and forest-clad mountains.

Burma is shut off from Assam on the north-west by a mass of densely forest-covered mountains, running in steep and high ridges, intersected by deep and narrow valleys, inhabited by the wildest tribes of the aboriginal inhabitants of our north-east frontier; Singphos and Nagas on the north, Karens farther to the north-east, Lushais and Chins on the north-west; all of them secure in their almost impenetrable jungles, through which no right of way from west to east exists, or ever has existed.

This little-known tract of country is perhaps the most interesting in India from the faunistic and botanical point of view.

This stretch of impassable hills is more or less continuous down the whole southern watershed of the Assam Valley; it envelops the little independent state of Manipur, and reaches into the Khasi and Garo plateau north of Sylhet and Tipperah to the west. One long arm stretches away southwards, and gradually separates the coast district of Arakan from the interior of Burma. The extreme north of Arakan is lost in the southern abutments of the long parallel mountain ridges of Lushai, which run from north to south and end on the sea-coast; whilst to the west are the Chittagong hill tracts and coast district. South of this, about the debouchment of the Arakan River (the Koladyne), which joins the sea near the trading port of Akyab, there is a stretch of coast lowland some 40 miles or so in width. Then this southern arm of the mountains becomes definitely detached as a single range, and strikes southwards, approaching nearer and nearer to the coast, narrowing the width of the Arakan lowlands until it ends as a barren red rocky ridge at Cape Negrais. This is usually known as the Arakan Range. The chief pass across it is the Aeng, of which the summit is about 5000 feet above sea. The western spurs of the mountains are covered with forests of fine timber, but on the east, where the range breaks down to the level of the Irrawady Valley in a succession of minor parallel ridges, bamboo is the principal growth.

East of the Arakan Range are the great central plains of lower Burma, watered by the Irrawady and the Sittang. East

of this again, extending through Burma from north to south, we find broken highlands and plateau, traversed by no definite mountain ranges, but forming one continuous chain of rugged tableland, stretching from the Kachin Hills on the north, through the northern and southern Shan states to the Karenni country on the south. This tableland is intersected by the trough of the Salween River. Beyond the Shan states is China in the north and Siam in the south. But the province of Burma does not end with the Shan states. There is a long strip of coast land, averaging perhaps 20 miles in width, but occasionally narrowing to 10, which extends down the western edge of the Malay peninsula, and includes the districts of Martaban and Tenasserim. This is also part of the province under the administration of the Lieutenant-Governor of Burma. It includes the Mergui archipelago, and is chiefly remarkable for the long broken coast-line, extending through 16 degrees of latitude, flanked by hundreds of islands which once formed part of the peninsula. The total length of Burmese coast-line from North Arakan to South Tenasserim is not much less than 550 miles. The total area of the province is 171,500 square miles, and its population (in 1891) was 7,600,000.

This brief outline of the configuration of the continent of India will suffice to make clear the allusions to the different provinces and forestry divisions of the country which follow hereafter.

The Island of Ceylon, though not included in the Indian Empire, must, from the geographical point of view, be regarded as a part of India. The latitude of its southern extremity is only six degrees north of the Equator. The extreme north latitude of the north-western corner of Kashmir is thirty-seven degrees north, and the altitude of the land surface of India varies from flats a few inches above sealevel to peaks 28,000 feet above it.

With the great variation in the elevation of the surface and the considerable distance involved from south to north, great variations in climate in the different parts of the country are a natural outcome. And, as a matter of fact, every variety of climate is to be found in the country and every condition of physical extremes from the Equatorial to the Arctic. And occasionally these sharp differences are found within close proximity the one to the other. As will be shown later the great changes in elevation and climate have a very marked

influence on the distribution of the numerous species of trees to be found in the forests of the country, varying with the different zones-hot moist, hot dry, arid, temperate and arctic.

Some account of the rainfall of the continent will be necessary here, since it exerts such a marked influence on the distribution and nature of the forest growth and general flora. As elsewhere in the tropics the rainfall in India has marked /characteristics, the feature of importance being the periodic rainfall or monsoons. The distribution and character of the various types of Indian forests are primarily influenced by the monsoon rainfall. The monsoons prevail at two seasons of the year. The first or south-west monsoon rains brings to an end the hot weather season, falling between June and September. They first strike and give rain to the whole of the lower western coast of the peninsula and the western coast of Bengal and Burma. The second or north-east monsoon falls between October and December, being chiefly confined to the eastern coast of the peninsula. Some parts of the country receive rain from one or other of the monsoons, other regions being affected by both. The southwest monsoon rains from the Arabian Gulf fall with their full force on the western coast districts from the Tapti southwards and the Ghát Range behind them; as also on the coast lands and outer hill ranges of Tenasserim, Pegu, Arakan and Chittagong; the plains of Bengal, the outer slopes of the Eastern Himalaya and the Khasi and Tipperah Hills. This monsoon also reaches in a lesser degree the western slopes of the Himalaya, the whole length of the outer southern parts of this great mountain system also receiving a monsoon rainfall at this period from the rain clouds travelling up from the Bay of Bengal. The north-east monsoon rains, on the other hand, provide the chief rainfall of the coast of the Carnatic, from the Kistna River southwards and inland to the outer ranges of the hills of the Eastern Gháts; of the Mysore tableland, the Javadi, etc., and even reach the edge of the Western Ghats. This region receives only a scanty and often failing supply of rain from the south-west monsoon. The regions which receive both monsoons are confined to the peninsula, the inner areas of the Deccan and the Carnatic. In addition to the monsoons, varying amounts of rainfall due to local precipitations are received in different parts of the country, as for instance the so-called "Christmas

"

rains in the United Provinces and elsewhere, the showers known as the Mango showers, and the local rainfall in Assam. These are often of very considerable local importance.

Omitting the part of the country in the south which is subject to two monsoons, the cold weather season commences in October or November (the former in the northern provinces) and lasts till the end of February or end of March respectively. This cold season is followed by the hot weather commencing in early March (or early April, the latter in the north) and lasting till the monsoon breaks in early June or July. It is during the hot season that the forests suffer so severely from fires; though the modern fire conservancy arrangements introduced by the Forest Department have done much to mitigate this evil. This season is, however, a somewhat trying one for the Forest Officer.

To complete these brief preliminary remarks a glance must be taken at the geology of this remarkable continent. It is in itself a fascinating study. To Oldham, of the Geological Survey of India, in his Evolution of Indian Geography (Vol. III, R.G.S.), we are indebted for an extremely able account of India's geological origin. It reads like a romance, whilst at the same time affording the Forester data which enable him to understand several important factors relative to tree distribution.

"Measured by the vast ages of geological existence, the peninsular area of India (the region of southern tableland) is by far the oldest. On the north-western borders of this area, stretching across the plains of Rajputana, are the remnants of a very ancient range of mountains called the Aravalli. To the south of these mountains the peninsula of India, as we know it now, has been a land area since the close of the paleozoic era. Across the extra peninsula regions to the northwest of the Aravalli Hills the sea has repeatedly flowed even to the commencement of tertiary ages; and between the two regions thus separated by the Aravallis there exists most striking differences both in structure and in conformation. The present shape of the peninsula-itself but a remnant of a far more widely extended continent-has only been assumed since the occurrence of the vast series of earth movements which resulted in the creation of the region of depression-the alluvial basins of the Indus and of the Ganges. Over the substratum of granite and gneiss which forms the bedrock of peninsular geologic structure, and eastward from the Aravallis, stretch the wide red sandstone deposits which are

« 上一頁繼續 »