Little is known of the course of the Irrawaddy River above Ava, and as it is joined by no large tributary near its mouth, its sectional area differs very little for hundreds of miles. At Prome, a distance of 190 miles in a direct line from the sea, the river is confined between two ranges of hills. The eastern range passes through the Tharawaddy district, separates the Irrawaddy from the Sittang Valley, and is lost in low undulating hills at Rangoon.