10*2 



Latitude. 



6g o'clock. 



10 o'clock. 



Noon. 



2 o'clock. 



5| o'clock. 



18° 53' 



17° 



21° 



22-4° 



22° 



18° 



16 19 



i 19 



22 



23-5 



23 



20*5 



13 51 



15 



16 



17 



17 



158 



I was unwilling to omit the last observation, 

 that of the 8th of July, though the sky, by a sin^ 

 gular anomaly, appeared that day as pale as we 

 see it on the continent in the temperate zone. 

 The Sun being at equal distances from the meri- 

 dian, the tints are deeper in the evening than in 

 the morning, without doubt because the maxi- 

 mum of temperature falls between the hours of 

 one and two. I have not remarked, like Mr. de 

 Saussure, that the cyanometer was regularly less 

 elevated at noon *, than some time before the 

 passage of the Sun across the meridian ; but I 

 have not been able to devote myself with the 

 same assiduity to this kind of investigation. 



We must not confound the cvanometrical 

 measures with the experiments, which Bouguer 

 attempted, by means of his lucimeter, on the in- 

 tensity of the light diffused or reflected by the 

 air. This intensity contributes without doubt 

 to modify the more or less azure tint of the 

 heavenly vault ; but the two phenomena do not 

 depend directly on the same causes, and there 



* Cyanometrical observations at Geneva : 



6 o'clock. 10 o'clock. Noon. 2 o'clock. 6 o'clock. 



14 7° 22 6° 22 5° 20 6° 17° 



