As a result of their isolation, the proportion of endemic plants is greater here than in any other region, and the great elevation of the mountains, with the consequent variation in temperature, moisture and barometric pressure, has multiplied the number of species.
The regular tides are hardly perceptible, but, under the influence of barometric pressure and wind, the sea-level occasionally varies as much as ft.
The middle region, to 14°-16° N., has variable winds in an area of low barometric pres- sure, while in the southern Red Sea south-east and east winds prevail.
The great range of the diurnal variation of barometric pressure during the afternoon hours, - which is the more striking, since at Rurki, Lahore, and other stations near the foot of the Western Himalayas this range is less than in the open plains.
(9) The velocity then should be independent of the barometric pressure, a result confirmed by observation.