It lies between Siam and the Bay of Bengal, enclosed by mountains on three sides, viz., the main chain of the Bilauktaung on the east, rising in places to 5000 feet, which, with its densely wooded spurs, forms an almost impassable barrier, between British and Siamese territory; the Nwahlabo in the centre, which takes its name from its loftiest peak (5000 ft.); and a third.
M.) and the innumerable smaller lakes which surround it being but relatively insignificant remains of the former lacustrine basins; while at the confluence of the Irtysh and the Ob impassable marshes stretch over many thousands of square miles.
For the rest there is a network of tracks, all practically impassable by wheeled vehicles, extending over the country and connecting the towns and villages one with another.
These conditions subsist with but few modifications, if any, from the Straits northward to the 42nd parallel, the extreme humidity, abnormal rainfall and dark skies being unfavourable to the development of insect life, while the Andes interpose an impassable barrier to migration from the countries of the eastern coast.
Principal Passes.-Though the Alps form a barrier they have never formed an impassable barrier, since, from the earliest days onwards, they have been traversed first, perhaps, for purposes of war or commerce, and later by pilgrims, students and tourists.
To every type of coast there may be related a special type of occupation and even of character; the deep and gloomy fjord, backed by almost impassable mountains, bred bold mariners whose only outlet for enterprise was seawards towards other lands - the viks created the vikings.
The Trengganu river is obstructed by impassable rapids at a distance of about 30 m.
Snares of another type consisting of a tangled mass of threads amongst which the spiders pick their way with ease, but which are impassable to insects, are spun by members of the Theridiidae and Pholcidae; but by common consent the so-called orbicular web, so characteristic of the Argyopidae but by no means confined to them, is regarded as manifesting the greatest perfection of instinct in snare-spinning.
The higher plateaus are called paramos, cold, windswept, mist-drenched deserts, lying between the elevations of 10,000 and 15,000 ft., which are often the only passes over the Cordilleras, and yet are almost impassable because of their morasses, heavy mists, and cold, piercing winds.
Above its normal level, and at this time forms an impassable barrier between the northern and central provinces.