Snow lies in some of the gorges all the year round.
Sometimes they occupy the approaches to tablelands, the narrowest points of gorges, or the fords of rivers; sometimes almost inaccessible mountain tops or important points on ridges; and it may be noticed that, where two important nuraghi are not visible from one another, a small one is interpolated, showing that there was a system of signalling from one to another.
They then form part of a system of ranges which curve north of the sources of the Chindwin river, and with the Kumon range and the hills of the Jade and Amber mines, make up a highland tract separated from the great Northern Shan plateau by the gorges of the Irrawaddy river.
Most of these main streams flow through profound gorges in a tropical climate, while the upper slopes yield products of the temperate zone, and the plateaus above are cold and bleak, affording only pasture and the hardiest cereals.
There is a tropical flora in the deep gorges, higher up a sub-tropical, then a temperate, then a sub-arctic flora.