422 PHYSICAL GEOGRAPHY AND CLIMATE. Chap. XX. 



had at Olenda. The maximum, at Olenda, I found 

 was 1481, temperature of the air 92° and 94°. The 

 rays of the sun were of the same power at ten a.m. 

 and five p.m., varying generally from 118° to 125°; 

 at noon, from 130° to 135°. 



These observations were taken in February and 

 March. Towards one o'clock, the maximum of heat 

 of the sun was attained. So it will be seen that the 

 sun had passed its maximum at one, while the maxi- 

 mum of the heat of the atmosphere occurred at three 

 o'clock. The greatest heat in the shade this year at 

 Mr. Bishop's observatory at Twickenham was 89°, 

 whilst the heat of the sun was 106° only ; this shows 

 the much less power of the sun in these latitudes 

 than in Equatorial Africa. 



Making these observations in the heat of the sun 

 were exceedingly exhausting, for I had to go near 

 my thermometer with only a cap on, so that no 

 shadow could fall upon it, and I could only carry 

 them on after intervals of two or three days, for 

 they generally produced a headache the next day. 



I remarked that sometimes a single cloud j)assing 

 over the sun, at the time of observation, would send 

 the thermometer down, in a few seconds, 8° or 10°, and 

 sometimes more. While at Mayolo, I carried on my 

 observations, almost at the same time, in an airy 

 verandah in the village and in the forest. I found 

 the temperature in the forest not varying more than 

 1° (cent.) from one to three o'clock, while sometimes 

 it had increased in an open space in the verandah 

 to 7° or 8° ; the temperature of the forest never 



