Chap. X5. HEAT OP THE SUN'S RAYS. 421 



higlier than 72°, but I saw it as low as 64° at six 

 o'clock a.m. The sky was constantly cloudy. But 

 it does not follow that, though the heat of the atmo- 

 sphere is less than in some other countries — the 

 reasons of which I have given — that the heat of the 

 sun would be less also ; at any rate, I hope that my 

 few observations may awaken the spirit of inquiry 

 on the subject, and that simultaneous observations 

 of the heat of the sun and of the atmosphere may 

 hereafter be made in different countries. 



But it will be necessary -first to adopt a uniform 

 sj'stem for ascertaining the power of the sun, and 

 I will raise my humble voice in favour of the sub- 

 ject being discussed. Unfortunately, there being no 

 general system for ascertaining the heat of the sun, 

 I used the one that appeared to me the most correct ; 

 so I am afraid I cannot compare my observations 

 with those of others. 



I had two thermometers, which I placed at some 

 distance from each other, sometimes fifty or one 

 hundred yards apart, sometimes nearer, and I was 

 surprised at the closeness of their results ;• a degree 

 was generally the maximum of difference. 



My thermometers were laid on a white board, in 

 order to avoid the moisture rising from the earth, 

 which was very great. I began these, observations 

 only in the Ashira country, and was not able to carry 

 them further, for my sun thermometers were stolen 

 on my journey between Ashira and Ofando-land. 

 The weather being warmer at Mayolo, I should have 

 found the thermometer marking higher still than I 



