244 Journal of the F.M.S. Museums. [Vol. X, 



of another type, known as the north-east and south-west 

 monsoons. From December to March the wind blows very 

 regularly from the north-east, and from May to October 

 it blows almost equally regularly from between south-east 

 and south-west. April and November are transition 

 months. 



To understand this change we must consider the 

 geographical position of Singapore. To the north lies the 

 great continent of Asia, to the south the large island of 

 Australia. These are far enough north and south to be 

 greatly cooled in winter and to a less extent heated in 

 summer. Lying in opposite hemispheres, Asia is hot while 

 Australia is cold, aiul nice nersa. The equatorial regions 

 are always hot. Now air expands with heat, and hot air 

 is lighter than cold air, consequently hot air tends to rise 

 while the cold air tlows along the surface of the earth to 

 replace it. In the months of November to March this cold 

 air flows in a steady stream of immense volume from the 

 high table lands of central Asia, where it is winter, across 

 the inter\'ening oceans to the equator and possibly beyond 

 it. This is the north-east monsoon, which returns every 

 year at about the same time. In some parts of the worjd 

 it blows with great force, but at Singapore it is relatively 

 light, blowing at only about two miles an hour a few feet 

 from the ground. 



From May to October it is Australia that is relatively 

 cold, and the wind at Singai>ore during these months is 

 away from this continent, i.e. is southerly, blowing from 

 between south-west and south-east at about two miles an 

 hour. At this sheltered locality calms are frequent but in 

 a more exposed situation calms are rarer and the velocity 

 of the wind somewhat greater. Wind generally increases 

 in velocity with height, and on a mountain slope there is 

 probably a fairly steady breeze which is a favourable factor 

 in the climate. The alternation of monsoons at the level 

 of 5,000 ft. is probably the same as at Singapore, but at 

 greater heights the wind would come very regularly from 

 east. 



5. Rainfall. 



The rainfall in the Straits Settlements is everyw^here 

 hea\^, Singapore having one hundred inches (2,500 

 millimetres) a year and Perak as much as 120 inches (3,000 

 nmi.) . Whether the rainfall at a mountain station of 

 5,000 ft. height would be more or less than this depends very 

 much on local conditions, probably it would be rather less, 

 as the heaviest rain clouds often have their under surfaces 

 below 5,000 ft. At still greater heights the amount falls 

 oft' rapidly. A total of one hundred inches is several times 

 as heavy as that of London, but it must be remembered 

 that owing to the extremely rapid rate at which rain falls 

 in the tropics, the actual time taken is ver>' much less. The 

 intensity of tropical rainfall is only rarely attained in 



