Between these ranges flow the rivers Meping, Mewang, Meyom and Menam, turbulent shallow streams in their upper reaches, but slow-moving and deep where they near the points of junction.
The nature of the breeding-place varies greatly according to the species, and while many of the mosquitoes that infest houses will breed even in the smallest accidental accumulation of water such as may have collected in a discarded bottle or tin, the larvae of other species less closely associated with man are found in natural pools or ditches, at the margins of slow-moving streams, in collections of water in hollow trees and bamboo-stumps, or even in the water-receptacles of certain plants.
Tests of a turbine of this slow-moving type showed an efficiency of 82% at full gate, and one of 75% when half of the passages in the guide-blades were closed by the shutters, as described above.
We may conveniently distinguish the two drifts as the slow-moving and fast-moving drifts respectively; but it should be remembered that, since these motions are measured relatively to the sun, this distinction is not physically significant.
Birds leave the slow moving river backwaters and streams and tend to move nearer to the coast for the winter.
