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



(4) But though the night is cooler than ti.e day, it U 

 still very hot, as judged by English standards. 74° F., 

 which is the average temperature of the coldest part of the 

 night at Singapore, would pass for a hot day in England. 



(5) It is in the extremes of temperature that the 

 difference between temperate and equatorial regions is 

 shown most markedly. Days almost as hot as any met 

 with in Singapore can be experienced in a L.ondon summer. 

 At Bukit Mertajam, near Perak, a maximum temperature 

 of 101° F. has been recorded, but this has been nearly 

 equalled in England (100° F.). On the other hand, the 

 lowest temperature recorded at Singapore is 70° F., while 

 at Richmond the thermometer has been down to 9° F., a 

 difference of 61.^ 



(6) The smaller difference from one day to the next 

 in the Tropics also makes for monotony. 



2. The Change of Temperature with Height. 



Leaving the sea-level- and climbing the slopes of a 

 mountain, the temperature is found to fall. This fall is 

 on the average at the rate of about 3 degrees Fahr. for 

 every tliousand feet. Thus at a height of five thousand feet 

 the mean temperature will have fallen from the tropical 

 figure of 80° F. to the merely pleasantly warm one of 65° F. 

 That is why it is always desirable in the troj)ics to establish 

 health stations or sanatoria on high mountains, the change 

 to the lower temperature having a marked bracing effect ; 

 the smaller density of the air owing to thf> decreased 

 atmospheric pressure is also beneficial at moderate 

 heights (not exceeding 6-7.000 ft.) as in the generally 

 greater dryness of the air. 



The diurnal range at high levels does not generally 

 diifer greatly from the average at lower levels, but much 

 depends upon local conditions. On an elevated plateau the 

 range is much greater than on the side of an isolated moun- 

 tain peak, for two reasons. Firstly, a plateau offers a wider 

 surface to direct heating by the sun's rays, and therefore 

 gets much hotter during the day than a mountain slope. 

 Secondly, on a level plateau the air becomes colder at night 

 than on a mountain slope. Air, especially div air, does 

 not itself lose heat rapidly by radiation, but the ground 

 beneath it does, and the air becomes cooled by contact with 

 the ground. Consequently air near the ground becomes 

 colder than that some distance away from the ground. 

 Gold air is heavier than warmer air, consequently it will flow 

 down a mountain slope like a river and give place to warmer 

 air which has not been in contact with the ground. On a 

 plateau it cannot flow away, but must remain v.here it is, 

 so that the temperature falls lower. 



This is illustrated by the contUtions at tw > mountain 

 stations in Java. One, on a level plateau enclosed by the 

 Yang Mountains, at an elevation of 6,500 ft., has a daily 



