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 deg. F. regularly for several weeks in April. The
rainfall in the hills varies very considerably, but seems to range from
about 60 in. in the broader valleys to about 300 in. on the higher
forest-clad ranges.

_Geology._--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 Irrawadd