so 85 90 



TEMPERATURE °F 



lOO 



I05 IIO 



Figure 2. 

 Monthly mean values of maximum temperatures (daily) and daily minimum of relative humidity 



possible to do even light work out-of-doors. If the relatively frequent occurrence 

 for 3-4 hours per day of conditions hotter than correspond to the line CC is to be 

 avoided, the mean temperature of the hottest month should not exceed 75°F in a dry 

 climate, or 73°F in a damp climate. This rule may be taken as a rough guide. 



At Beira on the Coast of Portuguese East- Africa, slightly north of latitude 20°, 

 the monthly mean values of minimum relative humidity vary between 59 and 63%, the 

 monthly mean maximum temperatures varying from 77.3°F to 89.6°F. All the months 

 from May to September are to the left of CC in Fig. 2, all the remaining months being 

 to the right of CC. Thus it is likely that normal office hours or light workout- of- 

 doors, would be possible from May to September inclusive, but would not be possible 

 during the remainder of the year. 



Among the data which I received from Mr Davies from East Africa were hourly 

 mean temperatures and relative humidities for each hour of the day, and month of 

 the year, for Chukwani, From these data it is possible to represent, on such a dia- 

 gram as that shown in Fig. 2, the mean diurnal variation of the conditions for each 



215 



