470
BURMA
of a rolling plateau there is a mass of broken hills. Except in the north, as is the case also west of the Salween, the hills are clad with dense forest. Burma may, therefore, be divided conveniently, but with no great precision, into (a) Northern Burma, including the Chin and Kochin hills, with a thin and miscellaneous alien population ; (b) Burma proper, which is practically the valley of the Irrawaddy after it ceases to be a gorge; and (c) the Shan tributary states. Burma proper is practically one great plain; the hills are comparatively mere undulations, and the one considerable peak, P6ppa, is volcanic. Still it is very different from the vast levels that stretch from the base of the Himalayas. It is rather a rolling upland interspersed with alluvial basins and sudden ridges of hills. The delta of the Irrawaddy begins near the village of Yegin Mingy, a few miles south of Myanaung. The sides of the delta measure 179 miles on the west and 126 miles on the east, and the base, measured from Elephant Point to Cape Negrais, is 137 miles in length, with an area of about 12,000 square miles. With the exception of the laterite hills near Myaungmya and the Eocene sandstone range near Thamandewa, in the same township, but more to the south, the whole of this area is a vast plain, gradually sloping down to the sea-shore. It is estimated that at least 2000 square miles, or one-sixth of this area, is below the level of the highest spring tides. This delta, together with the low-lying land to the east of the estuary of the Sittang, in the Pegu and Shwegyin districts, comprises what should from a physical point of view be considered as the lower province. The general aspect of these areas is the same. Till recent times they were covered with dense forest and bamboo jungle, and with water-logged swamps, clothed with elephant grass. The extension of cultivation and the draining of these swamps had changed the aspect of the country within the memory of persons living in 1901. Climate.—The climate of the delta is cooler and more temperate than in Upper Burma, and this is shown in the fairer complexion and stouter physique of the people of the lower province as compared with the inhabitants of the drier and hotter upper districts as far as Bhamo, where there is a great infusion of other types of the Tibeto-Burman family. North of the apex of the delta and the boundary between the deltaic and inland tracts, the rainfall gradually lessens as far as Nimbu, where what was formerly called the rainless zone commences and extends as far as Katha. Northward of this the annual rainfall increases till at Bhamo the average is about 70 inches, which is almost identical with that of Yegin Mingy. The physical conditions of the country are so varied that to give the mean annual rainfall of Burma would be simply misleading. The table in the next column shows (amongst other things) the mean annual rainfall for ten years in Lower Burma and for live years in Upper Burma. The scanty rainfall in the central zone between the 20th and 22nd parallels is caused chiefly by the Arakan range which drains the clouds, but also in no small degree by the want of forests, which is noticeable in all except the southern districts of this zone. The temperature varies almost as much as the rainfall. It is highest in the central zone, the mean of the maximum readings in such districts as Magwe, Myingyan, Kyaukse, Mandalay, and Shwebo in the month of May being close on 100° F., while in the littoral and sub-montane districts it is nearly ten degrees less. The mean of the minimum readings in December in the central zone districts is a few degrees under 60° F. and in the littoral districts a few degrees over that figure. In the hilly district of Mogok (Ruby Mines) the December mean minimum is 36'8° and the mean maximum 79°. The climate of the Chin and Kachin hills and also of the Shan States is temperate. In the shade and off the ground the thermometer rarely rises above 80° F. or falls below 25° F. In the hot season and in the sun as much as 150° F. is registered, and on the grass in the cold weather ten degrees of frost are not uncommon. Snow is seldom seen either in the Chin or Shan hills, but there are snow-clad ranges in the extreme north of the Kachin country. In the narrow valleys of the Shan hills, and especially in the Salween valley, the shade maximum reaches 100° F. regularly for several weeks in April. The rainfall in the hills varies very considerably, but seems to range from about 60 inches in the broader valleys to about 100 inches on the higher forest-clad ranges.
Table showing Mean Annual Rainfall and the character of different districts. Mean Annual Rainfall. ! Inches. Akyab .... 184-6 127-49 Northern Arakan Arakan 196-8 Kyaukpyu Sandoway. . 209-7 Rangoon Town [ 94-4 Hanthawaddy 116-66 Pegu . . Pegu . . . Tharrawaddy 87-5 43-9 Prome . Thongwa 86-7 110-3 Irrawaddy - Bassein 84-9 Henzada 36-9 Thayetmyo 182-2 Amherst 200-3 Tavoy . 183-7 Tenasserim- Mergui. 83-6 Toungoo Shwegyin 137-5 100-31 Salween 27Mandalay 70T06 Bhamo. Mandalay Katha . 46-97 83-88 Ruby Mine 30"289j Shwebo Sagaing 26-97 [ Sagaing. 28Lower Chindwin Upper Chindwin 73-587 23-18 Pakdkku 24T34 Minbu . Minbu 34-956 Magwe . 22Kyaukse 29Meiktila Meiktila 23Myingyan 42-213] Yamethin Division.
District.
Character of Country. Littoral. Sub-montane. Littoral. Deltaic. Central. Deltaic. Central. Littoral. Central. Deltaic. Sub-montane. Central. Sub-montane. Central. Sub-montane. Central. Sub-montane. Central. Central.
Geology.—The general parallelism of all the streams and hillranges gives an appearance of simplicity to the physical geology of the country, but owing to the prevalence of forest it has been found extremely difficult to determine the stratigraphy, and very little can be said to be actually known about the formations occurring. The Pegu Yoma consists entirely of the Miocene group, with beds of later Tertiary age, chiefly sandstone and shale, and the Arakan Yoma and the spurs to eastward and westward of the main range are chiefly of earlier Tertiary age, resting on Cretaceous and Triassic beds, which rise to the surface on the western face of the range. The Carboniferous limestone and its associated beds, together with the Mergui group, appear to run up the line of the Salween, and the main area of metamorphic rock lies to the east of all the other formations. The Burmese gneiss series consists of more or less granitoid gneiss, hornblendic gneiss, crystalline limestone, quartz and schists of various kinds. In many places the gneiss becomes a true granite. So far as is known there are two groups, the gneissose formation and limestone, which has been supposed to be of Lower Carboniferous age, but according to recent investigations more probably belongs to the Lower Silurian formations. Metamorphic rocks occupy a large but unexplored area in Upper Burma. They form all the higher ranges in the neighbourhood of Mandalay, and extend throughout a great portion of the country towards the Salween. Farther to the northward they extend from Bhamo to the neighbourhood of T’eng-yiieh (Momien) in Yunnan. The hills that skirt the Irrawaddy north ofMandalay are Silurian limestone, locally charged with crystalline limestone, which is the matrix of rubies, and metamorphic rocks composed ol gneiss and hornblendic schist, and opposite Kyaukmyaung greenstone and basalt are found. The Irrawaddy below Ava turns to the west and flows through recent rock formations, while the crystallines continue to the southward, forming a great part ol the Shan States and the Karen-ni country, and extending southwards into Tenasserim. The limestone, which is so conspicuous near Moulmein, extends northwards in large hills and ranges into Karen-ni and the Shan States. The abrupt cliffs, full of caves, characteristic of the formation, are very noticeable near Mong JNai (Myne) and northwards in the same latitude. The same formation is found eastwards of the Salween in Kengma, Kokang, Chenkang, and probably far northwards. It seems to belong to the Carboniferous series and to be identical, in part at least, with the lime stone found in the Mergui archipelago. Until the fossils are better known it is impossible to say whether the Burma series exactly corresponds to the Carboniferous beds of the Himalayas and the
