1832.] 
ISLAND OF SUMATRA. 
137 
deserts or plains to reflect back tlie rays of a vertical sun, as in 
the equatorial regions of Africa and South America, while the 
clayey qualities of tlje soil, and the thick luxuriant growth of 
verdure and forest, tend greatly to ameliorate the temperament of 
the atmosphere. Frost, snow, and hail are unknown ; but the 
vapours on the island are frequently dense, and clouds descend 
low ; while the morning fogs, which it requires several hours sun 
to dispel, lie between the hills, with outhnes well defined. 
All writers, from the earhest Portuguese voyagers, agree that 
this island and its vicinity are often visited, during the northwest 
monsoon, with most terrific tempests of thunder and lightning, 
scarcely surpassed in any other part of the world ; the whole 
appearing to tremble from the reiterated explosions; and the 
heavens, for hours at a time, presenting an expansive sheet of 
vivid fire. 
On the west coast of Sumatra, the southeast monsoon, or dry 
season, begins about May, and continues until about September. 
The northwest monsoon begins about November, and the heavy 
rains cease about March ; while the months of April and May, as 
well as October and November, are, generally distinguished on the 
coast by light and variable winds. The causes of "these periodical 
winds, which are known by the appellation of monsoons, as well 
as their influence on commercial operations, have often been 
alluded to by many able writers ; and they are of so much im- 
portance, and so necessary to be understood by the intelligent 
merchant, in selecting the seasons for sending his vessels into 
these seas, that we shall devote a chapter exclusively to this 
subject in another part of the work. 
The soil of Sumatra, generally speaking, is of a reddish stifl" 
clay, covered in most places with a dark rich mould, from which 
springs, spontaneously, a strong luxuriant vegetation of perpetual 
verdure. This manifests itself in various species of grass, shrub- 
bery, jungle, fruit-trees, and forests of timber, proportioned to 
the length of time the surface of the ground has remained undis 
turbed by agricultural or mining operations. In many places 
along the western coast of the island, are also extensive marshes, 
bogs, fens, or swamps, whose irregular and winding course may 
sometim.es be traced, in a continuous chain, for many miles, until' 
they terminate on the low margin of a river, a lake, or the sea 
