Geologically, British Burma consists of two divisions, an eastern and a western. The dividing line runs from the mouth of the Sittang river along the railway to Mandalay, and thence continues northward, with the same general direction but curving slightly towards the east. West of this line the rocks are chiefly Tertiary and Quaternary; east of it they are mostly Palaeozoic or gneissic. In the western mountain ranges the beds are thrown into a series of folds which form a gentle curve running from south to north with its convexity facing westward. There is an axial zone of Cretaceous and Lower Eocene, and this is flanked on each side by the Upper Eocene and the Miocene, while the valley of the Irrawaddy is occupied chiefly by the Pliocene. Along the southern part of the Arakan coast the sea spreads over the western Miocene zone. The Cretaceous beds have not yet been separated from the overlying Eocene, and the identification of the system rests on the discovery of a single Cenomanian ammonite. The Eocene beds are marine and contain nummulites. The Miocene beds are also marine and are characterized by an abundant molluscan fauna.
The Pliocene, on the other hand, is of freshwater origin, and contains silicified wood and numerous remains of Mammalia. Flint chips, which appear to have been fashioned by hand, are said to have been found in the Miocene beds, but to prove the existence of man at so early a period would require stronger evidence than has yet been brought forward.
The older rocks of eastern Burma are very imperfectly known. Gneiss and granite occur; Ordovician fossils have been found in the Upper Shan States, and Carboniferous fossils in Tenasserim and near Moulmein. Volcanic rocks are not common in any part of Burma, but about 50 m. north-north-east of Yenangyaung the extinct volcano of Popa rises to a height of 3000 ft. above the surrounding Pliocene plain. Intrusions of a serpentine-like rock break through the Miocene strata north of Bhamo, and similar intrusions occur in the western ranges. Whether the mud "volcanoes" of the Irrawaddy valley have any connexion with volcanic activity may be doubted. The petroleum of Burma occurs in the Miocene beds, one of the best-known fields being that of Yenangyaung. Coal is found in the Tertiary deposits in the valley of the Irrawaddy and in Tenasserim. Tin is abundant in Tenasserim, and lead and silver have been worked extensively in the Shan States. The famous ruby mines of Upper Burma are in metamorphic rock, while the jadeite of the Bhamo neighbourhood is associated with the Tertiary intrusions of serpentine-like rock already noticed.
The total population of Burma in 1901 was 10,490,624 as against 7,722,053 in 1891; but a considerable portion of this large increase was due to the inclusion of the Shan States and the Chin hills in the census area. Even in Burma proper, however, there was an increase during the decade of 1,530,822, or 19.8%. The density of population per square mile is 44 as compared with 167 for the whole of India and 552 for the Bengal Delta. England and Wales have a population more than twelve times as dense as that of Burma, so there is still room for expansion. The chief races of Burma are Burmese (6,508,682), Arakanese (405,143), Karens (717,859), Shans (787,087), Chins (179,292), Kachins (64,405) and Talaings (321,898); but these totals do not include the Shan States and Chin hills. The Burmese in person have the Mongoloid characteristics common to the Indo-Chinese races, the Tibetans and tribes of the Eastern Himalaya. They may be generally described as of a stout, active, well-proportioned form; of a brown but never of an intensely dark complexion, with black, coarse, lank and abundant hair, and a little more beard than is possessed by the Siamese. Owing to their gay and lively disposition the Burmese have been called "the Irish of the East," and like the Irish they are somewhat inclined to laziness.
Since the advent of the British power, the immigration of Hindus with a lower standard of comfort and of Chinamen with a keener business instinct has threatened the economic independence of the Burmese in their own country. As compared with the Hindu, the Burmese wear silk instead of cotton, and eat rice instead of the cheaper grains; they are of an altogether freer and less servile, but also of a less practical character. The Burmese women have a keener business instinct than the men, and serve in some degree to redress the balance. The Burmese children are adored by their parents, and are said to be the happiest and merriest children in the world.