176 
COMPENDIUM OF GEOGRAPHY AND TRAVEL 
Kampar, Bakan, and Indragiri, all of which form vast 
deltas with labyrinthine intersecting channels at their 
mouths. Upon the western side of the island the only 
river of importance is the Singkel, which debouches 
opposite Banyak Island, and is navigable for a consider¬ 
able distance by small vessels. 
4. Climate and Meterology. 
Sumatra differs considerably in its climate and rain¬ 
fall from Java. In the latter country—at all events in 
its eastern portion—a strong S.E. monsoon blows from 
March to November, which produces a marked degree of 
aridity, causing trees to shed their leaves and filling the 
air with powdery dust. This dry season, produced by 
the winds sweeping over the parched and heated deserts 
of the Australian continent, becomes less and less marked 
as we increase our distance from the latter country, until 
at the Straits of Sunda it becomes almost non-existent. 
The position of Sumatra, bisected as it is by the equator, 
causes the winds and seasons of Ache to differ from 
those of the Lampongs at the southern extremity. For 
at the north the monsoons blow from the north-east and 
south-west; in the centre is a wide belt of variable 
winds with alternating calms and squalls ; and in the 
south the monsoons blow from the south-east and north¬ 
west. A series of observations at Palembang show that 
from November to March the prevalent winds are westerly 
and north-westerly, this being the regular rainy season. 
April is the month of the change of the monsoons, when 
thunderstorms are most frequent. From May till Sep¬ 
tember easterly and south-easterly winds prevail, and the 
“ kentering,” or change of the monsoon, comes in September 
or October. During the shifting months of the S.E. 
